U.S. patent number 6,916,862 [Application Number 09/832,171] was granted by the patent office on 2005-07-12 for process for the preparation of pigment dispersion, pigment dispersion obtained by the same, ink jet recording ink comprising the same, and recording method and recorded material using the same.
This patent grant is currently assigned to Seiko Epson Corporation. Invention is credited to Kazuhiko Hara, Hidehiko Komatsu, Hitoshi Ota, Masahiro Yatake.
United States Patent |
6,916,862 |
Ota , et al. |
July 12, 2005 |
Process for the preparation of pigment dispersion, pigment
dispersion obtained by the same, ink jet recording ink comprising
the same, and recording method and recorded material using the
same
Abstract
Provided is a process for the preparation of a pigment
dispersion which comprises a pigment surface treatment step of
introducing at least one hydrophilic dispersibility-providing group
onto the surface of a pigment directly and/or with the
interposition of a polyvalent group, and a dispersion step of
dispersing a surface-treated pigment obtained at the surface
treatment step in an aqueous medium, characterized in that the
dispersion step involves the dispersion of the surface-treated
pigment in admixture with a wetting agent and water and a resin for
providing dispersibility and/or fixability is added during and/or
after the dispersion step.
Inventors: |
Ota; Hitoshi (Nagano,
JP), Komatsu; Hidehiko (Nagano, JP), Hara;
Kazuhiko (Nagano, JP), Yatake; Masahiro (Nagano,
JP) |
Assignee: |
Seiko Epson Corporation (Tokyo,
JP)
|
Family
ID: |
26589801 |
Appl.
No.: |
09/832,171 |
Filed: |
April 10, 2001 |
Foreign Application Priority Data
|
|
|
|
|
Apr 10, 2000 [JP] |
|
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2000-108359 |
Apr 6, 2001 [JP] |
|
|
2001-108788 |
|
Current U.S.
Class: |
523/200; 523/160;
523/205; 524/555; 524/588 |
Current CPC
Class: |
C09B
67/0002 (20130101); C09B 67/0017 (20130101); C09B
67/0019 (20130101); C09B 67/0022 (20130101); C09B
67/0023 (20130101); C09B 67/0086 (20130101); C09B
67/0089 (20130101); C09C 1/565 (20130101); C09D
11/322 (20130101); C01P 2004/64 (20130101); C01P
2004/62 (20130101) |
Current International
Class: |
C09B
67/00 (20060101); C09C 1/44 (20060101); C09D
11/00 (20060101); C09B 67/08 (20060101); C09B
67/46 (20060101); C09C 1/56 (20060101); C08K
009/00 (); C08K 009/04 (); C09D 011/10 (); C08L
083/00 (); C08L 033/26 () |
Field of
Search: |
;523/160,161,200,205
;524/495,556,577,588,555 ;106/31.6,31.89 |
References Cited
[Referenced By]
U.S. Patent Documents
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0688836 |
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10237349 |
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10330665 |
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10 330665 |
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1149974 |
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JP |
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11 049974 |
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11-246806 |
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00053902 |
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2000-053898 |
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2000 053902 |
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Feb 2000 |
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JP |
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00290578 |
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Oct 2000 |
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JP |
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20 00 290578 |
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Oct 2000 |
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JP |
|
20 00 351912 |
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Dec 2000 |
|
JP |
|
01/62862 |
|
Aug 2001 |
|
WO |
|
Other References
English language abstract of JP 10 330665, Dec. 15, 1998. Derwent
Publications Ltd., London; AN 1999-101283, XP002264023. .
English language abstract of JP 08 283596, Oct. 29, 1996. Derwent
Publications Ltd., London; AN 1997-017613, XP002264024. .
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29, 1997. .
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13, 1999. .
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14, 1999. .
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3, 1998. .
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16, 1999. .
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Feb. 22, 2000. .
English title and abstract of WO 01/62862, dated Aug. 30,
2001..
|
Primary Examiner: Shosho; Callie
Attorney, Agent or Firm: Ladas & Parry LLP
Claims
What is claimed is:
1. A process for the preparation of a pigment dispersion which
comprises a) a pigment surface treatment step of introducing at
least one hydrophilic dispersibility-providing group onto the
surface of a pigment directly and/or with the interposition of a
polyvalent group to form a surface treated pigment that is
self-dispersible in water and that comprises said at least one
hydrophilic dispersibility-providing group in an amount of not
lower than 10.times.10.sup.-6 per gram of particulate pigment, b) a
dispersion step of dispersing a surface-treated pigment obtained at
said surface treatment step in an aqueous medium, wherein said
dispersion step involves the dispersion of said surface-treated
pigment in admixture with a wetting agent and water, wherein the
wetting agent is selected from the group consisting of glycol
ethers, 1,2-(C.sub.4 -C.sub.10 alkyl)diols, 1,3-(C.sub.4 -C.sub.10
alkyl)diols, 1,5-(C.sub.4 -C.sub.10 alkyl)diols, and 1,6-(C.sub.4
-C.sub.10 alkyl)diols, and is present in amount that enhances a
dispersion efficiency of particles of the surface-treated pigment
in water, and (c) adding a resin for providing dispersibility an or
fixability during and/or after said dispersion step to form said
pigment dispersion, wherein the pigment dispersion has a liquid
component comprising polyvalent metal ions in a total amount of not
more than 600 ppm, wherein the dispersion step results in a
dispersion having a pigment concentration of from about 5 to 50% by
weight.
2. The process for the preparation of a pigment dispersion claim 1,
wherein the surface tension at 20.degree. C. of the mixture at said
dispersion step is not higher than 40 mN/m.
3. The process for the preparation of pigment dispersion according
to claim 1, wherein the wetting agent further comprises acetylene
glycols and/or acetylene alcohols in an amount of from not lower
than 1/50 of to twice the amount of said pigment by weight.
4. The process for the preparation of a pigment dispersion
according to claim 3, wherein said acetylene glycols and acetylene
alcohols are compounds represented by the following general
formulae (I) and (II), respectively: ##STR9##
wherein R.sup.1, R.sup.2, R.sup.1 and R.sup.4 each independently
represent an alkyl group; and the sum of m.sub.1 and n.sub.1 is
from 0 to 30; and ##STR10##
wherein R.sub.5 and R.sub.6 each independently represent an alkyl
group; and m.sub.2 is from to 30.
5. The process for the preparation of a pigment dispersion
according to claim 1, wherein said hydrophilic
dispersibility-providing group to be introduced onto the surface of
a pigment at said surface treatment step comprise at least one
selected from the group consisting of functional groups represented
by the following general formulae and salts thereof --OM, --COOM,
--CO--, --SO.sub.3 M, --SO.sub.2 M, --SO.sub.2 NH.sub.2,
--RSO.sub.2 M, --PO.sub.3 HM, --PO.sub.3 M.sub.2, --SO.sub.2 NHCOR,
--NH.sub.3, and --NR.sub.3 in which M represents a hydrogen atom,
alkaline metal, ammonium or organic ammonium; and R represents a
C.sub.1-12 alkyl group, a phenyl group which may have a substituent
or a naphthyl group which may have a substituent.
6. The process for the preparation of a pigment dispersion
according to claim 1, wherein said hydrophilic
dispersibility-providing group to be introduced onto the surface of
a pigment at said surface treatment step is a sulfur-containing
dispersibility-providing group.
7. The process for the preparation of a pigment dispersion
according to claim 1, wherein the amount of said resin to be added
is from not lower than 1/10 of to three times the amount of said
pigment by weight.
8. The process for the preparation of a pigment dispersion
according to claim 1, wherein said resin comprises an
alkali-soluble resin and/or a vinyl polymer obtained by the
copolymerization of (a) one or more selected from the group
consisting of silicon macromer represented by the following general
formula (III) and acrylamide or methacrylamide-based monomer
(excluding said monomer having salt-producing groups), (b) a
polymerizable unsaturated monomer having a salt producing group and
(c) a monomer copolymerizable with these monomers in the presence
of a radical polymerization initiator:
wherein X represents a polymerizable unsaturated group; Y
represents a divalent connecting group; R represents a hydrogen
atom, a lower alkyl group, an aryl group or an a alkoxy group, with
the proviso that a plurality of R's may be the same or different; Z
represent a monovalent siloxane polymer moiety having a
number-average molecular weight of at least about 500; v represents
0 or 1; and w represents an integer of from 1 to 3.
9. The process for the preparation of a pigment dispersion
according to claim 8, wherein among said resins, the alkali-soluble
resin is a styreneacryli c acid copolymer.
10. The process for the preparation of a pigment dispersion
according to claim 1, wherein said resin exhibits a glass
transition temperature of not lower than 50.degree. C.
11. The process for the preparation of a pigment dispersion
according to claim 1, wherein said resin has a weight-average
molecular weight of from 1,600 to 50,000.
12. The process for the preparation of a pigment dispersion
according to claim 1, wherein said resin exhibits an acid value of
from 10 to 250.
13. The process for the preparation of a pigment dispersion
according to claim 1, wherein Si, Ca, Mg, Fe, Cr and Ni ions
incorporated in the liquid component of the pigment dispersion are
each not higher than 100 ppm.
14. The process for the preparation of a pigment dispersion
according to claim 1, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises a carbon black pigment and/or an organic
pigment.
15. The process for the preparation of a pigment dispersion
according to claim 1, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises one or more pigments selected from the
group consisting of C.I. pigment red, C.I. pigment yellow, C.I.
pigment violet, C.I. pigment blue, C.I. pigment orange, C.I.
pigment green, and C.I. pigment brown.
16. The process for the preparation of a pigment dispersion
according to claim 1, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises one or more pigments selected from the
group consisting of phthalocyanine pigment, quinacridone pigment,
condensed azo pigment, isoindolinone pigment, quinophthalone
pigment, anthraquinone pigment, benzimidazolone pigment, and
perylene pigment.
17. The process for the preparation of a pigment dispersion
according to claim 1, wherein said surface treatment step involves
the of a polymer material onto the surface of a pigment directly
and/or with the interposition of a polyvalent group.
18. A pigment dispersion prepared by the process for the
preparation of a pigment dispersion described in claim 1.
19. An ink jet recording ink at least comprising the pigment
dispersion described in claim 18.
20. An ink jet recording method which comprises energizing the ink
described in claim 19 so that it is ejected from a recording head
and attached to a recording medium.
21. The ink jet recording method according to claim 20, wherein
said energy is a dynamic energy.
22. The ink jet recording method according to claim 20, wherein
said energy is a heat energy.
23. A recorded material obtained by the method described in claim
20.
24. The process according to claim 1, wherein the wetting agent is
present in an amount of from 0.1 to 30% by weight based on the
weigh of the pigment dispersion in the dispersion step.
25. A process for the preparation of a recording liquid comprising
the steps of (i) providing a pigment dispersion prepared by the
process of claim 1; and
(ii) subsequent to the preparation of said pigment dispersion,
mixing the pigment dispersion with at least a solvent to form the
recording liquid.
26. The process as claimed in claim 25, wherein step (ii) comprises
mixing the pigment dispersion with at least the solvent, a
surfactant and water to form the recording liquid.
27. The process as claimed in claim 26, wherein the recording
liquid has a solid component comprising the surface treated pigment
and resin and a liquid component comprising the wetting agent,
solvent, surfactant, polyvalent metal ions and water, the solid
component of the recording liquid being present in an amount by
weight that is less than an amount by weight of the wetting agent,
solvent, surfactant and polyvalent metal ions present in the liquid
component of the recording liquid.
28. The process as claimed in claim 27, wherein the pigment
dispersion has (i) a liquid component comprising the wetting agent,
water and polyvalent metal ions and (ii) a solid component
comprising the surface treated pigment the resin, said solid
component being present in the pigment dispersion in an amount by
weight that is greater than a total amount by weight of the wetting
agent and polyvalent metal ions present in the liquid
component.
29. The process according to claim 28, wherein the pigment
dispersion consists essentially of the surface treated pigment, the
resin, the wetting agent, the polyvalent metal ions and water.
30. The process according to claim 28, wherein the pigment
dispersion consists essentially of the surface treated pigment, the
resin, the wetting agent, a neutralizing agent, the polyvalent
metal ions and water.
31. The process according to claim 1, the resin is added during
said dispersion step.
32. A process for the preparation of a pigment dispersion which
comprises: (a) a pigment surface treatment step of introducing at
least one hydrophilic dispersibility-providing group onto the
surface of a pigment directly and/or with the interposition of a
polyvalent group to form a surface treated pigment that is
self-dispersible in water and that comprises said at least one
hydrophilic dispersibility-providing group in an amount of not
lower than 10.times.10.sup.-6 equivalent per gram of particulate
pigment, (b) a dispersion step of dispersing a surface treated
pigment obtained at said surface treatment step in an aqueous
medium, wherein said dispersion step involves the dispersion of
said surface-treated pigment in admixture with a wetting agent and
water wherein the wetting agent is selected from the group
consisting of acetylene glycols, acetylene alcohols, glycol ethers
and alkylene glycols and is present in an amount that enhances a
dispersion efficiency of particles of the surface-treated pigment
in water, and (c) adding a resin for providing dispersibility
and/or fixability during and/or after said dispersion step to form
said pigment dispersion, wherein the pigment dispersion has a
liquid component comprising polyvalent metal ions in a total amount
of not more than 600 ppm, wherein the dispersion step results in a
dispersion having a pigment concentration of from about 5 to 50% by
weight; and wherein said resin comprises a vinyl polymer obtained
by the copolymerization of (a) one or more selected from the group
consisting of silicon macromer represented by the following general
formula (III) and acrylamide or methacrylamide-based monomer
(excluding said monomer having salt-producing groups), (b) a
polymerizable unsaturated monomer having a salt producing group and
(c) a monomer copolymerizable with these monomers in the presence
of a radical polymerization initiator:
wherein X represents a polymerizable unsaturated group; Y
represents a divalent connecting group; R represents a hydrogen
atom, a lower alkyl group, an aryl group or an alkoxy group, with
the proviso that a plurality of R's may be the same or different; Z
represents a monovalent siloxane polymer moiety having a
number-average molecular weight of at least about 500; v represents
0 or 1; and w represents an integer of from 1 to 3.
33. The process for the preparation of a pigment dispersion
according to claim 32, wherein the surface tension at 20.degree. C.
of the mixture at said dispersion step is not higher than 40
mN/m.
34. The process for the preparation of a pigment dispersion
according to claim 32, wherein the wetting agent comprises
acetylene glycols and/or acetylene alcohols in an amount of from
not lower than 1/50 of to twice the amount of said pigment by
weight.
35. The process for the preparation of a pigment dispersion
according to claim 34, wherein said acetylene glycols and acetylene
alcohols are compound represented by the following general formulae
(I) and (II), respectively: ##STR11## wherein R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 each independently represents an alkyl group;
and the sum of m.sub.1 and n.sub.1 is from 0 to 30; and
##STR12##
wherein R.sup.5 and R.sup.6 each independently represents an alkyl
group; and m.sub.2 is from 0 to 30.
36. The process for the preparation of a pigment dispersion
according to claim 32, wherein said hydrophilic
dispersibility-providing group to be introduced onto the surface of
a pigment at said surface treatment step comprise at least one
selected from the group consisting of functional groups represented
by the following general formulae and salts thereof --OM, --COOM,
--CO--, --SO.sub.3 M, --SO.sub.2 M, --SO.sub.2 NH.sub.2,
--RSO.sub.2 M, --PO.sub.3 HM, --PO.sub.3 M.sub.2, --SO.sub.2 NHCOR,
--NH.sub.3, and --NR.sub.3 in which M represents a hydrogen atom,
alkaline metal, ammonium or organic ammonium; and R represents a
C.sub.1-12 alkyl group, a phenyl group which may have a substituent
or a naphthyl group which may have a substituent.
37. The process for the preparation of a pigment dispersion
according to claim 32, wherein said hydrophilic
dispersibility-providing group surface of a pigment at said surface
treatment step is a sulfur-containing dispersibility providing
group.
38. The process for the preparation of a pigment dispersion
according to claim 32, wherein the amount of said resin to be added
is from not lower than 1/10 of to three times the amount of said
pigment by weight.
39. The process for the preparation of a pigment dispersion
according to claim 32, wherein said resin exhibits a glass
transition temperature of not lower than 50.degree. C.
40. The process for the preparation of a pigment dispersion
according to claim 32, said resin has a weight-average molecular
weight of from 1,600 to 50,000.
41. The process for the preparation of a pigment dispersion to
claim 32, wherein said resin exhibits an acid value of from 10 to
250.
42. The process for the preparation of a pigment dispersion
according to claim 32, wherein Si, Ca, Mg, Fe, Cr and Ni ions
incorporated in the liquid component of the pigment dispersion and
are not higher than 100 ppm.
43. The process for the preparation of a pigment dispersion
according to claim 32, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises a carbon black pigment and/or an organic
pigment.
44. The process for the preparation of a pigment dispersion
according to claim 32, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises one or more pigments selected from the
group consisting of C.I. pigment red, C.I. pigment yellow, C.I.
pigment violet, C.I. pigment blue, C.I. pigment orange, C.I.
pigment green, and C.I. pigment brown.
45. The process for the preparation of a pigment dispersion
according to claim 32, wherein said pigment for introducing a
hydrophilic dispersibility-providing group at said surface
treatment step comprises one or more pigments selected from the
group consisting of phthalocyanine pigment, quinacridone pigment,
condensed azo pigment, isoindolinone pigment, quinophthalone
pigment, anthraquinone pigment, benzimidazolone pigment, and
perylene pigment.
46. The process for the preparation of a pigment dispersion
according to claim 32, wherein said surface treatment step involves
the introduction of a polymer material onto the surface of a
pigment directly and/or with the interposition of a polyvalent
group.
47. A pigment dispersion prepared by the process for the
preparation pigment dispersion according to claim 32.
48. An ink jet recording ink at least comprising the pigment
dispersion according to claim 47.
49. An ink jet recording method which comprises energizing the ink
according to claim 48 so that it is ejected from a recording lead
and attached to a recording medium.
50. The ink jet recording method according to claim 49, wherein
said energy is a dynamic energy.
51. The ink jet recording method according to claim 49, wherein
said energy is a heat energy.
52. A recorded material obtained by the method described in claim
49.
53. The process according to claim 32, wherein the wetting agent is
present in an amount of from 0.1 to 30% by weight based on the
weight of the pigment dispersion in the dispersion step.
54. A process for the preparation of a recording liquid comprising
the steps of: (i) providing a pigment dispersion prepared by the
process of claim 32; and (ii) subsequent to the preparation of said
pigment dispersion, mixing the pigment dispersion with at least a
solvent to form the recording liquid.
55. The process as claimed in claim 54, wherein step (ii)
comprising mixing the pigment dispersion with at least the solvent,
a surfactant and water to form the recording liquid.
56. The process as claimed in claim 55, wherein the recording
liquid has a solid component comprising the surface treated pigment
and resin and a liquid component comprising the wetting agent,
solvent, surfactant, polyvalent metal ions and water, the solid
component of the recording liquid being present in an amount by
weight that is less than an amount by weight of the wetting agent,
solvent surfactant and polyvalent metal ions present in the
liquid.
57. The process as claimed in claim 56, wherein the pigment
dispersion has (i) a liquid component comprising the wetting agent,
water and polyvalent metal ions and (ii) a solid component
comprising the surface treated pigment and the resin, said solid
component being present in the pigment dispersion in an amount by
weight that is greater than a total amount by weight of the wetting
agent and polyvalent metal ions present in the liquid
component.
58. The process according to claim 57, wherein the pigment
dispersion consists essentially of the surface treated pigment, the
resin, the wetting agent, the polyvalent metal ions and water.
59. The process according to claim 57, wherein the pigment
dispersion consists essentially of the surface treated pigment, the
resin, the wetting agent, neutralizing agent, the polyvalent metal
ions and water.
60. The process according to claim 32, wherein the resin is added
during said dispersion step.
61. A process for the preparation of a recording liquid comprising
the steps of: (i) providing a pigment dispersion prepared by a
process comprising a) a pigment surface treatment step of
introducing at least one hydrophilic dispersibility-providing group
onto the surface of a pigment directly and/or with the
interposition of a polyvalent group to form a surface treated
pigment that is self dispersible in water and that comprises said
at least one hydrophilic dispersibility-providing group in an
amount of not lower than 10.times.10.sup.-6 equivalent per gram of
particulate pigment, b) a dispersion step of dispersing a
surface-treated pigment obtained at said surface treatment step in
an aqueous medium, wherein said dispersion step involves the
dispersion of said surface-treated pigment in admixture with a
wetting agent and water wherein the wetting agent is selected from
the group consisting of acetylene glycols, acetylene alcohols,
glycol ethers and alkylene glycols and is present in an amount that
enhances a dispersion efficiency of particles of the
surface-treated pigment in water, and (c) adding a resin for
providing dispersibility an or fixability during and/or after said
dispersion step to form said pigment dispersion, wherein the
pigment dispersion has a liquid component comprising polyvalent
metal ions in a total amount of not more than 600 ppm, wherein the
dispersion step results in a dispersion having pigment
concentration of from about 5 to 50% by weight; and (ii) subsequent
to the preparation of said pigment dispersion, mixing the pigment
dispersion with at least a solvent to form the recording liquid,
wherein step (ii) comprises mixing the pigment dispersion with at
least the solvent, a surfactant and water to form the recording
liquid, and wherein the recording liquid has a solid component
comprising the surface treated pigment and resin and a liquid
component comprising the wetting agent, solvent, surfactant,
polyvalent metal ions and water, the solid component of the
recording liquid being present in an amount by weight that is less
than an amount by weight of the wetting agent, solvent, surfactant
and polyvalent metal ions present in the liquid component of the
recording liquid.
Description
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of a
pigment dispersion which can be preferably used as an "ink for ink
jet printer" which is given an ejection energy such as dynamic
energy by a piezoelectric element or heat energy by a heating
element to be ejected from a recording head, a pigment dispersion
obtained by the process, an ink jet recording ink comprising the
pigment dispersion, and a recording method and a recorded material
using the ink.
The present invention also relates to a process for the preparation
of a pigment dispersion which can be used for various purposes such
as ink solution for fountain pen, ball-point pen, felt pen and
other writing utensils, coating compound for use in air brushing or
the like and industrial coating solution, a pigment dispersion
obtained by such a preparation process, and a pigment ink
comprising such a pigment dispersion.
BACKGROUND OF THE INVENTION
As a colorant for ink for ink jet printer there has heretofore been
mainly used a dye. In recent years, the use of pigments having
excellent fastness has been studied. Recorded matters obtained with
a pigment as a colorant are superior to that obtained with a dye in
respect to fastness such as water fastness and light fastness.
On the other hand, unlike a dye, a pigment is not dissolved in
water. Therefore, many studies have been made of the use of, as a
colorant for aqueous ink, a pigment in the form of dispersion of
particles having a dispersant such as resin adsorbed thereto
(hereinafter, this kind of pigment will be referred to as
"dispersant type pigment"). For example, JP-A-2000-290578 (The term
"JP-A" as used herein means an "unexamined published Japanese
patent application") discloses a process for the preparation of an
aqueous pigment dispersion which comprises a step of dry-grinding a
pigment containing coarse particles in the presence of a
water-soluble resin, and a step of adding a nonionic surface active
agent containing acetylene group to the dry-ground material
obtained at the dry-grinding step so that it is dispersed in water.
Further, JP-A-2000-351912 discloses a process for the preparation
of a pigment composition which comprises dry-grinding a pigment
containing coarse particles in the presence of a nonionic surface
active agent containing acetylene group and a water-soluble resin
or dry-grinding a pigment containing coarse particles in the
presence of a nonionic surface active agent containing acetylene
group, adding a water-soluble resin to the ground material, and
then further dry-grinding the material.
However, even the methods disclosed in the above cited
JP-A-2000-290578 and JP-A-2000-351912 are disadvantageous in that
the dispersant type pigment can be difficultly kept dispersed
stably in an aqueous medium. Thus, the dispersant is separated from
the surface of the pigment, causing the pigment particles to be
agglomerated to each other or sedimented. Further, if the particle
diameter is relatively great, the pigment particles undergoes
spontaneous sedimentation due to its weight. Thus, the colorant
stays dispersed in particulate form, causing troubles.
In general, an ink for ink jet printer comprises a colorant and
water as well as various solvents and surface active agents.
Therefore, the conventional method involving the dispersion of a
dispersant type pigment in an aqueous solvent can difficultly keep
the pigment particles stably dispersed in particulate form. In
particular, when the ink comprises a penetrating agent providing a
strong penetrating effect incorporated therein to enhance the rate
at which it dries on the recording medium, the separation of the
dispersant from the surface of the particulate pigment can be
possibly accelerated, further deteriorating dispersion
stability.
Under the circumstances, various techniques which comprises
rendering a pigment itself water-dispersible have been proposed.
For example, JP-A-10-195360and JP-A-10-330665 propose a
self-dispersible carbon black having a hydrophilic group such as
carboxyl group, carbonyl group, sulfone group and hydroxyl group
bonded to the surface thereof directly or with the interposition of
a polyvalent group. Further, JP-A-8-3498, JP-A-10-195331, and
JP-A-10-237349 propose that carbon black be subjected to surface
treatment for the improvement of dispersibility thereof. Moreover,
JP-A-8-283598, JP-A-10-110110, and JP-A-10-110111 propose a
surface-treated pigment having a sulfone group introduced onto the
surface of an organic pigment.
Further, JP-A-11-49974 discloses that an organic pigment mass which
can be positively charged on the surface thereof is prepared by
treating an organic pigment mass having a sulfonic acid group
introduced therein with a monovalent metal ion. Further, an aqueous
ink composition having an excellent storage stability comprising a
particulate pigment prepared from this surface-positively charged
organic pigment mass, a dispersant and water is disclosed.
JP-A-2000-53902 proposes an ink comprising as a colorant a
particulate pigment (macromolecular chromophore) having a
water-solubilizing functional group and a polymer provided on the
surface thereof with the interposition of benzene ring introduced
onto carbon black.
An ink for ink jet printer is required to exhibit various physical
properties. It is particularly important to secure the ink itself
with desired storage stability and secure desired ejectability
(prevention of clogging, deflected flying, etc.) during ink jet
recording. The ink is also required to provide excellent print
quality (high print density, printed image having little feathering
and bleeding, etc.) with respect to recording paper. In other
words, as an ink for ink jet printer, such an ink is required to
satisfy all the requirements for ink physical properties,
ejectability and print quality at the same time.
Since the foregoing self-dispersible surface-treated pigment has a
dispersible group chemically bonded to the surface thereof, the
dispersible group cannot be separated therefrom even if the
foregoing penetrating agent is incorporated in the ink. Therefore,
the foregoing self-dispersible surface-treated pigment is excellent
in storage stability such as dispersion stability and thus can
easily meet various requirements for ink for ink jet printer.
However, an ink jet printer which can print a high precision image
at a high speed has been recently desired. Thus, the ink jet
printer has been required to eject an extremely fine ink dot at a
higher frequency. Accordingly, in order to secure stabilized print
properties, the ink used must meet further requirements.
Unlike the ink comprising a dye, the pigment ink having particles
dispersed therein, even if it is a self-dispersible pigment ink
having excellent basic properties, can difficultly meet both the
requirements for stabilized ejectability and storage stability.
Further, even if the pigment is a self-dispersible pigment, the
colorant still stays dispersed. Accordingly, the problem that
sedimentation occurs when the diameter of dispersed particles is
great remains unsolved.
Further, the arrangement comprising a foregoing surface-treated
pigment alone is disadvantageous in that the pigment has no fixing
components provided on the surface thereof, providing insufficient
image fixability. In order to cope with this problem,
JP-A-10-110129 discloses that a water-soluble resin is added to
improve fixability.
However, the ink composition disclosed in JP-A-10-110129 is
disadvantageous in that when printed on a gloss medium requiring an
image quality which is equal to or higher than that of color
photograph (e.g., gloss paper, gloss film), it can difficultly
penetrate into the recording medium. As a result, the liquid
component in the ink can little penetrate into the recording
medium, leaving the pigment particles behind on the surface of the
recording medium and hence impairing the smoothness and gloss of
the surface of the image. Thus, the print quality is impaired.
Further, the resulting image has an insufficient fixability.
Moreover, the foregoing ink is disadvantageous in that it causes
bleeding on the area where two or more color inks are imposed on
each other or come into contact with each other during full color
printing.
SUMMARY OF THE INVENTION
The present invention has been worked out in the foregoing problems
of the prior art. An object of the present invention is to provide
a process for the preparation of a pigment dispersion which can
provide stable printing properties even with the modern ink jet
printer designed for higher image quality and higher speed
operation, exhibits a good storage stability, provides good gloss
and fixability even when printed on a gloss media in particular,
provides high print quality having little feathering and bleeding
and undergoes minimized sedimentation, a pigment dispersion
obtained by this method, an ink jet recording ink comprising this
pigment dispersion, and a recording method and a recorded matter
using this ink.
Another object of the present invention is to provide a pigment
dispersion which can be used for various purposes such as ink
solution for fountain pen, ball-point pen, felt pen and other
writing utensils, coating compound for use in air brushing or the
like and industrial coating solution, a pigment dispersion obtained
by such a preparation process, and a pigment ink comprising such a
pigment dispersion.
In the course of studies of conditions of preparation of a pigment
dispersion comprising a surface-treated pigment under which the
foregoing printing properties, storage stability and sedimentation
properties required for ink for ink jet printer are satisfied, the
inventors found that it is important to add a proper wetting agent
at a step of dispersing a self-dispersible surface-treated pigment
in an aqueous medium to form a mixture state in which dispersion is
effected.
On the basis of the foregoing results, the inventors made extensive
studies of conditions under which further storage stability and
sedimentation properties can be attained and required gloss and
fixability of an ink attaining these requirements on a gloss medium
can be satisfied. As a result, it was found extremely important to
add a specific resin for providing dispersibility and/or fixability
during or after the foregoing dispersion step.
The present invention is based on the foregoing knowledge.
The process for the preparation of a pigment dispersion according
to the present invention comprises a pigment surface treatment step
of introducing at least one hydrophilic dispersibility-providing
group onto the surface of a pigment directly and/or with the
interposition of a polyvalent group, and a dispersion step of
dispersing a surface-treated pigment obtained at the surface
treatment step in an aqueous medium, characterized in that the
dispersion step involves the dispersion of the surface-treated
pigment in admixture with a wetting agent and water and a resin for
providing dispersibility and/or fixability is added during and/or
after the dispersion step.
Preferred embodiments of the process for the preparation of a
pigment dispersion according to the present invention include: The
surface tension of the mixture at the dispersion step is not higher
than 40 mN/m. The pigment concentration in the mixture at the
dispersion step is not higher than 50% by weight as calculated in
terms of weight. The wetting agent to be used at the dispersion
step comprises one or more materials selected from the group
consisting of acetylene glycols, acetylene alcohols, glycol ethers
and alkylene glycols. The total amount of the acetylene glycols
and/or acetylene alcohols to be added as a wetting agent at the
dispersion step is from not lower than 1/50 of to not higher than
twice the amount of said pigment. The acetylene glycols and
acetylene alcohols are compounds represented by the following
general formulae (I) and (II), respectively: ##STR1##
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 each independently
represent an alkyl group; and the sum of m.sub.1 and n.sub.1 is
from 0 to 30. ##STR2##
wherein R.sup.5 and R.sup.6 each independently represent an alkyl
group; and m.sub.2 is from 0 to 30.
Further embodiments of the process for the preparation of a pigment
dispersion according to the present invention include: The
hydrophilic dispersibility-providing group to be introduced onto
the surface of a pigment at the surface treatment step comprises at
least one selected from the group consisting of functional groups
represented by the following general formulae and salts
thereof:
--OM, --COOM, --CO--, --SO.sub.3 M, --SO.sub.2 M, --SO.sub.2
NH.sub.2, --RSO.sub.2 M, --PO.sub.3 HM, --PO.sub.3 M.sub.2,
--SO.sub.2 NHCOR, --NH.sub.3, --NR.sub.3 (in which M represents a
hydrogen atom, alkaline metal, ammonium or organic ammonium; and R
represents a C.sub.1-12 alkyl group, a phenyl group which may have
a substituent or a naphthyl group which may have a substituent).
The hydrophilic dispersibility-providing group to be introduced
onto the surface of a pigment at the surface treatment step is a
sulfur-containing dispersibility-providing group.
Still further embodiments of the process for the preparation of a
pigment dispersion according to the present invention include: The
amount of the resin to be added is from not lower than 1/10 of to
three times the amount of said pigment by weight. The resin
comprises an alkali-soluble resin and/or a vinyl polymer obtained
by the copolymerization of one or more selected from the group
consisting of silicon macromer represented by the following general
formula (III) and acrylamide or methacrylamide-based monomer
(excluding base-producing groups), a polymerizable unsaturated
monomer having a salt-producing group and a monomer copolymerizable
with these monomers in the presence of a radical polymerization
initiator:
wherein X represents a polymerizable unsaturated group; Y
represents a divalent connecting group; R represents a hydrogen
atom, a lower alkyl group, an aryl group or an alkoxy group, with
the proviso that a plurality of R's may be the same or different; Z
represents a monovalent siloxane polymer moiety having a
number-average molecular weight of at least about 500; v represents
0 or 1; and w represents an integer of from 1 to 3.
Still further embodiments of the process for the preparation of a
pigment dispersion according to the present invention include: The
resin exhibits a glass transition temperature of not lower than
50.degree. C. The resin has a weight-average molecular weight of
from 1,600 to 50,000. The resin exhibits an acid value of from 10
to 250. Among the resins, the alkali-soluble resin is a
styrene-acrylic acid copolymer. The total amount of polyvalent
metal ions to be incorporated in the liquid component of the
pigment dispersion thus prepared is not higher than 600 ppm. The
amount of Si, Ca, Mg, Fe, Cr and Ni ions to be incorporated in the
liquid component of the pigment dispersion thus prepared are each
not higher than 100 ppm.
Still further embodiments of the process for the preparation of a
pigment dispersion according to the present invention include: The
pigment for introducing a hydrophilic dispersibility-providing
group at the surface treatment step comprises a carbon black
pigment and/or an organic pigment. The pigment for introducing a
hydrophilic dispersibility-providing group at the surface treatment
step comprises one or more pigments selected from the group
consisting of C.I. pigment red, C.I. pigment yellow, C.I. pigment
violet, C.I. pigment blue, C.I. pigment orange, C.I. pigment green,
and C.I. pigment brown. The pigment for introducing a hydrophilic
dispersibility-providing group at the surface treatment step
comprises one or more pigments selected from the group consisting
of phthalocyanine pigment, quinacridone pigment, condensed azo
pigment, isoindolinone pigment, quinophthalone pigment,
anthraquinone pigment, benzimidazolone pigment, and perylene
pigment. The surface treatment step involves the introduction of a
polymer material onto the surface of a pigment directly and/or with
the interposition of a polyvalent group.
On the other hand, the pigment dispersion is prepared by the
foregoing preparation process and comprises at least a
surface-treated pigment, a penetrating agent, and a resin for
providing dispersibility and/or fixability.
The ink jet recording ink comprises the foregoing pigment
dispersion.
The ink jet recording method according to the present invention
comprises energizing an ink according to claim 22 so that it is
ejected from a recording head and attached to a recording
medium.
Preferred embodiments of the ink jet recording method according to
the present invention include: The energy is a dynamic energy. The
energy is a heat energy. The recorded material according to the
present invention is obtained by the foregoing ink jet recording
method.
The term "self-dispersible pigment" as used herein is meant to
indicate a "particulate pigment which can be dispersed in a solvent
by it self". The self-dispersible pigment doesn't mean a
"dispersible pigment" which can be dispersed only by the effect of
a dispersant such as resin adsorbed by the surface of a particulate
pigment but means a "self-dispersible surface-treated pigment
(herein occasionally referred simply to as "surface-treated
pigment") which has a hydrophilic dispersibility-providing group
chemically bonded to the surface of a particulate pigment to make
itself dispersible in water. (The term "particulate pigment" as
used hereinafter essentially indicates a "secondary pigment
particle".
In the invention, the use of the foregoing self-dispersible
surface-treated pigment as an ink colorant makes it possible to add
as much as necessary a penetrating agent of the kind which has
heretofore been restricted in its use because it impairs the
dispersion stability of conventional dispersible pigments.
Accordingly, a fast-drying ink which exhibits an enhanced
capability of penetrating into the recording medium can be
provided, making it possible to realize a printed image having
little feathering and bleeding. Further, the content of the pigment
as a colorant can be increased by the amount of the dispersant
which is not added. Moreover, even when the pigment concentration
is the same, the ink of the invention can provide a high print
density as compared with the conventional dispersible pigment ink,
making it easy to meet the requirements for higher image quality
involving the enhancement of color developability.
The term "wetting agent" as used herein is meant to indicate an
agent for dispersing a surface-treated pigment or slurry or wet
cake of surface-treated pigment obtained at the surface treatment
step in an aqueous solution (particularly ion-exchanged water or
distilled water) to obtain a dispersion. This wetting agent has an
effect of making it easy for the particulate pigment to have a good
affinity for (wet with) the aqueous medium as well as increasing
the contact resistance of pigment particles with each other or the
dispersing medium to raise the dispersion efficiency. As a result,
the conditions under which the apparatus performs shearing at the
dispersion step can be relaxed (the shearing force to be given from
the apparatus to the pigment dispersion can be lowered) Further,
the time required for dispersion can be reduced.
The term "liquid component of ink" as used herein is meant to
indicate a liquid portion which holds a solid portion such as
particulate pigment in the ink in dispersion. Accordingly, the
"liquid component" contains impurities mixed in the vehicle (liquid
portion in the ink itself) during the preparation of the ink.
By subjecting the ink to centrifuging so that it is divided into a
supernatant component and a sedimented component, and then
measuring the supernatant component by some known method, the
amount of various polyvalent metal ions such as Si, Ca, Mg, Fe, Cr
and Ni ions contained in the foregoing "liquid component" can be
measured. The term "polyvalent metal ion" as used herein is meant
to indicate a metal ion having a valence of two or more.
DETAILED DESCRIPTION OF THE INVENTION
Mode for Carrying Out the Invention
Pigment
As the pigments to be incorporated in the pigment dispersion and
pigment ink of the invention there can be exemplified the following
pigments.
Examples of inorganic black pigments employable herein include
carbon black (C.I. pigment black 7) such as furnace black, lamp
black, acetylene black and channel black.
Examples of pigments which can be used mainly as yellow pigments
include C.I. pigment yellow 1 (Hanza Yellow G), 2, 3 (Hanza Yellow
10G), 4, 5 (Hanza Yellow 5G), 6, 7, 10, 11, 12 (Disazo Yellow AAA),
13, 14, 16, 17, 24 (Flavanthrone Yellow), 55 (Disazo Yellow AAPT),
61, 61:1, 65, 73, 74 (Fast Yellow 5GX), 81, 83 (Disazo Yellow HR),
93 (condensed azo yellow 3G), 94 (condensed azo yellow 6G), 95
(condensed azo yellow GR), 97 (Fast Yellow FGL), 99
(Anthraquinone), 100, 108 (Anthrapyrimidine Yellow), 109
(Isoindolinone Yellow 2GLT), 110 (Isoindolinone Yellow 3RLT), 117,
120 (Benzimidazolone Yellow H2G), 123 (Anthraquinone Yellow), 124,
128 (condensed azo yellow 8G), 129, 133, 138 (Quinophthalone
Yellow), 139 (Isoindolinone Yellow), 147, 151 (Benzimidazolone
Yellow H4G), 153 (Nickel Nitroso Yellow), 154 (Benzimidazolone
Yellow H3G), 155, 156 (Benzimidazolone Yellow HLR), 167, 168, 172,
173 (Isoindolinone Yellow 6GL), and 180 (Benzimidazolone
Yellow).
Examples of magenta pigments employable herein include C.I. pigment
red 1 (Para Red), 2, 3 (Toluidine Red), 4, 5 (ITR Red), 6, 7, 8, 9,
10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38
(Pyrazolone Red B), 40, 41, 42, 88 (Thioindigo Bordeaux), 112
(Naphthol Red FGR), 114 (Brilliant Carmine BS), 122 (Dimethyl
Quinacridone), 123 (Perylene Vermillion), 144, 146, 149 (Perylene
Scarlet), 150, 166, 168 (Anthanthrone Orange), 170 (Naphthol Red
F3RK), 171 (Benzimidazolone Maroon HFM), 175 (Benzimidazolone Red
HFT), 176 (Benzimidazolone HF3C), 177, 178 (Perylene Red), 179
(Perylene Maroon), 185 (Benzimidazolone Carmine HF4C), 187, 188,
189 (Perylene Red), 190 (Perylene Red), 194 (Perylene Red), 202
(Quinacridone Mazenta), 209 (Dichloroquinacridone Red), 214
(condensed Azo Red), 216, 219, 220 (Condensed Azo), 224 (Perylene
Red), 242 (condensed Azo Scarlet), 245 (Naphthol Red), C.I. Pigment
violet 19 (Quinacridone), 23 (Dioxazine Violet), 31, 32, 33, 36,
38, 43, and 50.
Examples of cyan pigments employable herein include C.I. pigment
blue 15, 15:1, 15:2, 15:3, 15:4, 15:6 (Phthalocyanine Blue), 16
(metal-free Phthalocyanine Blue), 17:1, 18 (Alkali Blue Toner), 19,
21, 22, 25, 56, 60 (Threne Blue), 64 (Dichloroindanthrone Blue), 65
(Violanthrone), and 66 (Indigo).
As organic black pigments there may be used organic black pigments
such as Aniline Black (C.I. pigment black 1).
Further examples of organic pigments other than yellow, cyan and
magenta pigments include C.I. pigment orange 1, 2, 5, 7, 13, 14,
15, 16 (Valcan Orange), 24, 31 (condensed Azo Orange 4R), 34, 36
(Benzimidazolone Orange HL), 38, 40 (Pyranthrone Orange), 42
(isoindolinone Orange RLT), 43, 51, 60 (Benzimidazolone-based
insoluble monoazo pigment), 62 (benzimidazone-based insoluble
monoazo pigment), 63; C.I. pigment green 7 (Phthalocyanine Green),
10 (Green Gold), 36 (chlorinated phthalocyanine green), 34, 47
(Violanthrone Green); C.I. pigment brown 1, 2, 3, 5, 23 (condensed
Azo Brown 5R), 25 (Benzimidazolone Brown HFR), 26 (Perylene
Bordeaux), and 32 (Benzimidazolone Brown HFL).
The pigment dispersion to be used in the invention and the ink
comprising the pigment dispersion may comprise one or more of the
foregoing pigments incorporated therein in combination.
Surface-treated Pigment (Self-dispersible Pigment)
The surface-treated pigment obtained by the process for the
preparation of a pigment dispersion of the invention comprises a
functional group or salt thereof as a hydrophilic
dispersibility-providing group introduced onto (chemically bonded
to) the surface of the particulate pigment directly or with the
interposition of a polyvalent group to render itself dispersible in
water in the absence of dispersant.
In the invention, a single functional group or a plurality of
functional groups may be introduced on to one pigment particle. The
kind of the functional group to be introduced onto the surface of
the particulate pigment and the degree of introduction of the
functional group may be properly determined taking into account the
dispersion stability in the ink, the color density of the ink, the
dryability of the ink on the front surface of the ink jet head,
etc.
The functional group to be introduced as a hydrophilic
dispersibility-providing group may comprise one or more functional
groups selected from the group consisting of functional groups and
salts thereof represented by the following general formulae:
--OM, --COOM, --CO--, -SO.sub.3 M, --SO.sub.2 M, --SO.sub.2
NH.sub.2, --RSO.sub.2 M, --PO.sub.3 HM, --PO.sub.3 M.sub.2,
--SO.sub.2 NHCOR, --NH.sub.3, --NR.sub.3 (in which M represents a
hydrogen atom, alkaline metal, ammonium or organic ammonium; and R
represents a C.sub.1-12 alkyl group, a phenyl group which may have
a substituent or a naphthyl group which may have a
substituent).
In the case where the hydrophilic dispersibility-providing group is
introduced onto the surface of the pigment with the interposition
of a polyvalent group, examples of the polyvalent group to which
the dispersibility-providing group is bonded include a C.sub.1-12
alkylene group, a phenylene group which may have a substituent, and
a naphthylene group which may have a substituent.
As the surface treatment method which comprises introducing the
foregoing functional group or salt thereof as a hydrophilic
dispersibility-providing group onto the surface of the particulate
pigment directly or with the interposition of a polyvalent group
there may be used any of various known surface treatment
methods.
Examples of these known surface treatment methods include (a) a
method which comprises allowing ozone or sodium hypochlorite
solution to act on a commercially available oxidized carbon black
so that it is further subjected to oxidation and hence further
hydrophilic treatment on the surface thereof (as disclosed in
JP-A-7-258578, JP-A-8-3498, JP-A-10-120958, JP-A-10-195331,
JP-A-10-237349), (b) a method which comprises treating carbon black
with 3-amino-N-alkyl-substituted pyridium bromide (as disclosed in
JP-A-10-195360, JP-A-10-330665), (c) a method which comprises
dispersing an organic pigment in a solvent in which the organic
pigment is insoluble or can be difficultly dissolved, and then
treating the dispersion with a sulfonating agent to introduce a
sulfone group onto the surface of the particulate pigment (as
disclosed in JP-A-8-283596, JP-A-10-110110, JP-A-10-110111), (d) a
method which comprises dispersing an organic pigment in a basic
solvent which forms a complex with sulfur trioxide, adding sulfur
trioxide to the dispersion so that the organic pigment is subjected
to surface treatment, whereby a sulfone group or sulfonamino group
is introduced onto the surface thereof (as disclosed in
JP-A-10-110114), and (e) a method which comprises azo coupling
reaction so that a water-solubilizing functional group and a
polymer are introduced onto the surface of a pigment with the
interposition of a phenylene group connected to carbon black (as
disclosed in JP-A-2000-53902).
However, the process for the preparation of the surface-treated
pigment to be used in the invention is not limited to the foregoing
methods (a) to (e).
The sulfur-containing dispersibility-providing group to be used as
a hydrophilic dispersibility-providing group in the invention is
not specifically limited so far as such. a functional group
containing sulfur atom and providing water dispersibility. Specific
examples of such a sulfur-containing dispersibility-providing group
include sulfinic acid group (SO.sub.2.sup.-), and sulfonic acid
group (SO.sub.3.sup.-).
The foregoing hydrophilic dispersibility-providing group to be
introduced onto the surface of the surface-treated pigment may be
present at least on the surface of the particulate pigment or may
be contained in the particulate pigment.
The surface-treated pigment obtained by the process for the
preparation of a pigment dispersion according to the invention may
comprise a polymer material introduced onto (chemically bonded to)
the surface of the particulate pigment directly or with the
interposition of a polyvalent group. The introduction of the
polymer material onto the surface of the pigment can be easily
accomplished with the interposition of a polyvalent group. The
reaction can be realized by acylation reaction or nucleophilic
substitution reaction of ester group.
Specific examples of such a polymer material include polyethylene
glycol, polypropylene glycol, polytetramethylene glycol, and
homologs thereof (monoalkyl ethers such as polyethylene glycol,
polypropylene glycol and polytetramethylene glycol having an alkyl
group moiety having from 1 to 10 carbon atoms, monoaryl ethers,
amines of methoxypolyethylene glycol, polyvinyl alcohol, copolymers
of polyvinyl alcohol with polyvinyl acetate). These polymer
materials each preferably are terminated by at least one amine
group or hydroxyl group.
When the pigment dispersion having the foregoing polymer material
introduced onto the surface thereof and the ink comprising the
pigment dispersion are used, the adsorptivity of the resin
providing dispersibility and/or fixability described later is
further enhanced, making it possible to exert an effect of further
improving sedimentation properties and fixability on the recording
medium during printing.
Wetting Agent
The wetting agent to be used in the process for the preparation of
a pigment dispersion according to the invention will be described
hereinafter. When the wetting agent of the invention is added at
the step of dispersing the surface-treated pigment in an aqueous
solvent, the efficiency of dispersion of pigment can be
enhanced.
The wetting agent exerts an effect of attaining a good affinity for
(wet with) the aqueous medium as well as increasing the contact
resistance of pigment particles with each other in an aqueous
medium to raise the dispersion efficiency when added during the
dispersion of the surface-treated pigment in an aqueous medium
(ion-exchanged water or distilled water). As a result, the
conditions under which the apparatus performs shearing at the
dispersion step can be relaxed (the shearing force to be given from
the apparatus to the pigment dispersion can be lowered). Further,
the time required for dispersion can be shortened. Moreover, the
amount of contaminants such as polyvalent metal ion in the
dispersion can be reduced.
As the wetting agent to be used in the invention there may be used
any wetting agent without any restriction so far as it has an
effect of enhancing the dispersion efficiency as mentioned above.
Particularly preferred examples of wetting agent employable herein
include acetylene glycols, acetylene alcohols, glycol ethers, and
alkylene glycols. Other examples of wetting agent employable herein
include lower alcohols, and nonionic surface active agents.
Further, other alcohols, water-soluble organic solvents, anionic
surface active agents, cationic surface active agents, amphoteric
surface active agents, and saccharides may be used singly or in
combination of two or more thereof.
Specific examples of acetylene glycols and acetylene alcohols which
can be used as wetting agents include compounds represented by the
following general formulae (I) and (II). ##STR3##
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently
represent an alkyl group; and the sum of m.sub.1 and n.sub.1 is
from 0 to 30. ##STR4##
wherein R.sup.5 and R.sup.6 each independently represent an alkyl
group; and m.sub.2 is from 0 to 30.
Specific examples of trade name of these compounds include Surfynol
TG, Surfynol 104, Surfynol 420, Surfynol 440, Surfynol 465,
Surfynol 485, Surfynol 61, Surfynol 82 (produced by Air Products
Inc.), and Acetylenol E-H, Acetylenol E-L, and Acetylenol E-O
(produced by Kawaken Fine Chemicals Co., Ltd.).
The (total) amount of acetylene glycols and/or acetylene alcohols
to be added at the dispersion step is preferably from not lower
than 1/50 of to not higher than twice the amount of the pigment by
weight.
When the added amount of the acetylene glycols and/or acetylene
alcohols falls below 1/50 of the amount of the pigment, a
sufficient dispersing effect can not be occasionally obtained. On
the contrary, when the acetylene glycols and/or acetylene alcohols
are added in a large amount (e.g., more than several times the
amount of the pigment) the ink having a desired pigment
concentration prepared from this pigment dispersion shows a greater
surface tension drop than required and thus can wet and spread in
the vicinity of the ink jet head, making it difficult to secure
stabilized ejection properties.
In order to minimize the amount of the wetting agent to be
incorporated in the ink comprising this pigment dispersion or
suppress the penetrating power of the ink, acetylene alcohols
having a small molecular weight can be used as a wetting agent. For
example, when Surfynol 61 as mentioned above is used as a wetting
agent, it can be evaporated when the dispersion is heated after the
dispersion step to minimize the residual amount of the wetting
agent.
Examples of glycol ethers which can be preferably used as wetting
agents include diethylene glycol mono (C.sub.4-8 alkyl) ether,
triethylene glycol mono (C.sub.4-8 alkyl)ether, propylene glycol
mono(C.sub.3-6 alkyl) ether, and propylene glycol mono (C.sub.3-6
alkyl) ether. Specific examples of these glycol ethers include
diethylene glycol mono-n-butyl ether, triethylene glycol
mono-n-butyl ether, propylene glycol mono-n-butyl ether, and
dipropylene glycol mono-n-butyl ether.
Specific other examples of glycol ethers employable herein include
ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
ethylene glycol monobutyl ether, ethylene glycol monomethyl ether
acetate, diethylene glycol monomethyl ether, diethylene glycol
monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene
glycol mono-iso-propyl ether, diethyleneglycolmono-iso-propyl
ether, ethylene glycol mono-n-butyl ether, ethylene glycol
mono-n-butyl ether, diethylene glycol mono-tert-butyl ether,
1-methyl-1-methoxybutanol, propylene glycolmonomethyl ether,
propylene glycol monoethyl ether, propylene glycol mono-tert-butyl
ether, propylene glycol mono-n-propyl ether, propylene glycol
mono-iso-propyl ether, dipropylene glycol monomethyl ether,
dipropylene glycol monoethyl ether, dipropylene glycol
mono-n-propyl ether, and dipropylene glycol mono-iso-propyl
ether.
Examples of the alkylene glycols which can be used as wetting
agents include 1,2-(C.sub.4-10 alkyl)diol, 1,3-(C.sub.4-10 alkyl)
diol, 1,5-(C.sub.4-10 alkyl)diol, and 1,6-(C.sub.4-10 alkyl)diol.
Specific examples of these alkylene glycols include
1,2-pentanediol, 1,2-hexanediol, 1,3-butanediol, 1,5-pentanediol,
and 1,6-hexanediol.
The foregoing glycol ethers and/or alkylene glycols have a wetting
effect as well as dissolving aid properties. In other words, among
the foregoing acetylene glycols, a compound which exhibits a low
solubility in water by itself can be used in combination with
glycol ethers to enhance its solubility, making it possible to
increase the added amount thereof.
Further, since the foregoing glycol ethers and/or alkylene glycols
have no little bactericidal activity, it can inhibit the
proliferation of microorganism, fungi, etc. when it is incorporated
in the dispersion and ink. Accordingly, by adding these glycol
ethers and/or alkylene glycols as wetting agents at the dispersion
step in an amount of not lower than a predetermined value (several
percents by weight), the proliferation of these microorganisms can
be inhibited without newly adding germicides or preservatives.
Specific other examples of the wetting agent employable herein
include lower alcohols such as methanol, ethanol, 1-propanol,
2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl
alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol,
isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, and
neopentyl alcohol.
Examples of nonionic surface active agents which can be used as
wetting agents include fluorine-based copolymer, silicone-based
copolymer, acrylic acid copolymer, polyoxyethylene alkyl ether,
polyoxyethylene alkyl phenyl ether, polyoxyethylene secondary
alcohol ether, polyoxyethylene sterol ether, polyoxyethylene lauryl
ether, polyoxyethylene lanoline derivative, ethylene oxide
derivative of alkylphenol formalin condensate, polyoxyethylene
polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene
alkyl ether, fatty acid ester of polyoxyethylene compound,
polyethylene oxide-condensed polyethylene glycol fatty acid ester,
fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan
fatty acid ester, propylene glycol fatty acid ester, sucrose fatty
acid ester, fatty acid alkanolamide, polyoxyethylene fatty acid
amide, polyoxyethylene alkylamine, and alkylamine oxide.
Further specific examples of wetting agents employable herein
include water-soluble organic solvents such as ethylene glycol,
diethylene glycol, triethylene glycol, propylene glycol,
tetraethylene glycol, polyethylene glycol, dipropylene glycol,
polypropylene glycol, hexylene glycol, thiodiglycol, glycerin and
1,2,6-hexanetriol. Examples of alcohols which can be used as
wetting agents include 1-henxanol, 2-methyl-1-pentanol,
4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol,
3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-nonanol,
3,5,5-trimethyl-1-hexanol, and 1-decanol.
Examples of anionic surface active agents employable herein include
higher fatty acid salt, higher alkyldicarboxylic acid salt, higher
alcohol sulfuric acid ester, higher alkylsulfonic acid salt,
alkylbenzenesulfonic acid salt, alkylnaphthalenesulfonic acid salt,
salt of naphthalenesulfonic acid (with Na, K, Li, Ca), formalin
polycondensate, condensate of higher fatty acid with amino acid,
dialkylsulfosuccinic acid ester, alkylsulfosuccinic acid salt,
naphthenic acid salt, alkylethercarboxylic acid salt, acylated
peptide, .alpha.-olefinsulfonic acid salt, N-acylmethyltaurin,
alkylethersulfuric acid salt, higher secondary alcohol ethoxy
sulfate, sodium salt of polyoxyethylene alkyl phenyl ether sulfuric
acid, ammonium salt of polyoxyethylene alkyl phenyl ether sulfuric
acid, monoglysulfate, alkyletherphosphoric acid ester, and
alkylphosphoric acid ester.
Examples of cationic surface active agents which can be used as
wetting agents include aliphatic amine salt, quaternary ammonium
salt, sulfonium salt, and phosphonium salt. Examples of amphoteric
surface active agents which can be used as wetting agents include
carboxybetaine type surface active agent, aminocarboxylic acid
salt, and lecithin. Examples of saccharides which can be used as
wetting agents include glucose, mannose, fructose, ribose, xylose,
arabinose, lactose, galactose, maltitol, sorbitol, gluconolactone,
and maltose.
Specific examples of wetting agents employable herein have been
given above, but the present invention should not be construed as
being limited thereto.
Resin Providing Dispersibility and/or Fixability
The process for the preparation of a pigment dispersion according
to the invention is also characterized by the use of a "resin
providing dispersibility and/or fixability" besides the foregoing
surface-treated pigment and wetting agent.
The resin providing dispersibility and/or fixability employable
herein is not specifically limited so far as it exerts the
desirable effect. A resin providing dispersibility alone or a resin
providing fixability alone may be individually added. A resin which
can be adsorbed to the surface of the surface-treated pigment
without impairing the dispersibility thereof is desirable.
In the invention, the use of the foregoing "resin providing
dispersibility and/or fixability" is advantageous in that the use
of a resin providing dispersibility makes it possible to further
improve the storage stability (particularly sedimentation
properties) of the pigment dispersion while the use of a resin
providing fixability makes it possible to improve the fixability
and gloss of an ink comprising the pigment dispersion.
In particular, the use of a resin providing dispersibility and
fixability at the same time is more advantageous in that further
improvement of storage stability of the pigment dispersion and an
ink comprising same and improvement of print quality (particularly
fixability and gloss) of printed image can be accomplished at the
same time. The use of such a resin eliminates the necessity of
adding resin which exhibit respective properties during the
preparation of ink, lessening the limit of the added amount of ink
described later and hence making it easy to prepare an ink
composition particularly having a desired viscosity which can be
ejected from the ink jet head in a stable manner.
As the foregoing resin to be used in the process for the
preparation of a pigment dispersion according to the invention
there may be preferably used an alkali-soluble resin and/or a vinyl
polymer obtained by the copolymerization of one or more selected
from the group consisting of silicon macromer represented by the
following general formula (III) and acrylamide or
methacrylamide-based monomer (excluding base-producing groups), a
polymerizable unsaturated monomer having a salt-producing group and
a monomer copolymerizable with these monomers in the presence of a
radical polymerization initiator:
wherein X represents a polymerizable unsaturated group; Y
represents a divalent connecting group; R represents a hydrogen
atom, a lower alkyl group, an aryl group or an alkoxy group, with
the proviso that a plurality of R's may be the same or different; Z
represents a monovalent siloxane polymer moiety having a
number-average molecular weight of at least about 500; v represents
0 or 1; and w represents an integer of from 1 to 3.
The glass transition temperature (hereinafter referred to as "Tg")
of the foregoing resin is preferably not lower than 50.degree. C.
When Tg of the resin is not lower than 50.degree. C., the resulting
printed image exhibits a good fixability at actual temperature
(generally lower than 50.degree. C.). When Tg of the resin falls
below 50.degree. C., the resulting printed image tends to exhibit a
deteriorated fixability at actual temperature. In some cases, the
printed image doesn't exhibit desired fixability.
The weight-average molecular weight (hereinafter referred to as
"Mw") of the foregoing resin is preferably from 1,600 to 50,000.
When Mw of the resin falls within this range, the resulting printed
image can be provided with sufficient fixability and gloss.
Further, an ink having a viscosity such that it can be ejected from
the ink jet head in a stable manner can be easily prepared.
The acid value (hereinafter referred to as "AV") of the foregoing
resin is preferably from 10 to 250. When AV of the resin falls
within this range, the resin exhibits a good solubility or
dispersibility in the pigment dispersion and an ink comprising
same. Further, the resulting printed image can be kept fairly
waterproof.
Examples of the molecular structure of alkali-soluble resin among
the foregoing resins include copolymer of acrylic acid and styrene,
copolymer of acrylic acid ester and methacrylic acid, copolymer of
acrylic acid and methacrylic acid ester, and copolymer of styrene
and maleic acid.
Particularly preferred among these molecular structures is
styrene-acrylic acid copolymer because it exhibits a good
adsorptivity to the surface of the surface-treated pigment to
further improve the dispersibility thereof. The styrene-acrylic
acid copolymer is desirable also because it exhibits a good
solubility in the foregoing wetting agent and thus doesn't cause
the production of foreign matters derived there from even after
prolonged storage of the pigment dispersion and an ink comprising
same. The styrene-acrylic acid copolymer is desirable also because
the image printed with such an ink can be provided sufficient
fixability or gloss.
Referring further to the resin to be used in the process for the
preparation of a pigment dispersion according to the invention, as
the alkali-soluble resin having the foregoing desired "Tg, Mw, AV
and molecular structure" there may be used a commercially available
product. Examples of the commercially available product employable
herein include Joncryl 68 (Tg: 70.degree. C.; Mw: 10,000; AV: 195),
Joncryl 679 (Tg: 85.degree. C.; Mw: 7,000; AV: 200), Joncryl 680
(Tg: 60.degree. C.; Mw: 3,900; AV: 215), Joncryl 682 (Tg:
57.degree. C.; Mw: 1,600; AV: 235), Joncryl 550 (Tg: 75.degree. C.;
Mw: 7,500; AV: 200), Joncryl 555 (Tg: 75.degree. C.; Mw: 5,000; AV:
200), Joncryl 586 (Tg: 63.degree. C.; Mw: 3,100; AV: 105), Joncryl
683 (Tg: 63.degree. C.; Mw: 7,300; AV: 150), and Joncryl B-36 (Tg:
65.degree. C.; Mw: 6,800; AV: 250) (all produced by Johnson Polymer
Corporation).
As the resin providing dispersibility and/or fixability to be used
in the process for the preparation of a pigment dispersion
according to the invention there may be used a vinyl copolymer
obtained by the copolymerization of one or more selected from the
group consisting of silicon macromer represented by the foregoing
general formula (III) and acrylamide or methacrylamide-based
monomer (excluding base-producing groups), a polymerizable
unsaturated monomer having a salt-producing group and a monomer
copolymerizable with these monomers in the presence of a radical
polymerization initiator, besides the foregoing alkali-soluble
resin.
Referring to the foregoing specific vinyl polymer, X in the silicon
macromer represented by the foregoing general formula (III)
represents a polymerizable unsaturated group. Specific examples of
such a polymerizable unsaturated group include CH.sub.2.dbd.CH--,
and CH.sub.2.dbd.C(CH.sub.3)--. Y represents a divalent connecting
group. Specific examples of such a divalent connecting group
include --COO--, --COOC.sub.b H.sub.2b -- (in which b represents an
integer of from 1 to 5), and phenylene group. Preferred among these
divalent connecting groups is --COOC.sub.3 H.sub.6 --.
R represents a hydrogen atom, lower alkyl group such as methyl and
ethyl, aryl group such as phenyl, or alkoxy group such as methoxy.
Preferred among these groups is methyl group. Z represents a
monovalent cyloxane polymer moiety having a number-average
molecular weight of at least about 500. Preferred among these
monovalent siloxane polymers is a monovalent dimethylsiloxane
polymer having a number-average molecular weight of from 800 to
5,000. The suffix v is 0 or 1, preferably 1. The suffix w is an
integer of from 1 to 3, preferably 1. As such a silicon macromer
there is preferably used a Type FM-0711 silicon macromer (trade
name, produced by CHISSO CORPORATION).
Examples of the acrylamide monomer or methacrylamide monomer free
of salt-producing group employable herein include acrylamide
monomers such as acrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide
(diacetone acrylamide), N,N-dimethylacrylamide,
N,N-diethylacrylamide, N,N-diisopropyl acrylamide,
N,N-dibutylacrylamide, N,N-diphenylacrylamide,
N-tert-butylacrylamide, N-tert-hexylacrylamide, N-tert-octyl
acrylamide, N-(1-methylundecyl)acrylamide, N-isobornyl acrylamide,
N-norbonylacrylamide, N-adamanthylacrylamide, N-benzylacrylamide,
N-(4-methylphenyl)methylacrylamide, N-diphenylacrylamide,
phthaliraidemethylacrylamide, acrylamidehydroxyacetic acid,
3-acrylamide-3-methylbutanic acid, 10-acrylamide-undecylic acid,
N-(2,2,2-trichloro-1-hydroxy)ethylacrylamide,
N-(1,1,3,5-tetramethyl) octylacrylamide,
N-(1,5-dimethyl-1-ethyl)hexylacrylamide, N-iso-propylacrylamide,
N-methylolacrylamide, N-cyclohexyl acrylamide and
N-(1,1,3-trimethyl)butylacrylamide, and methacrylamide monomers
such as methacrylamide, N-(1,1-dimethyl-3-oxobutyl)methacrylamide,
N,N-diisopropylmethacrylamide N,N-diethyl methacrylamide,
N,N-diisopropylmethacrylamide, N,N-dibutylmethacrylamide,
N,N-diphenylmethacrylamide, N-tert-butylmethacrylamide,
N-tert-hexyl methacrylamide, N-tert-octylmethacrylamide,
N-(1-methylundecyl)methacrylamide, N-isobornylmethacrylamide,
N-norbornyl methacrylamide, N-adamanthylmethacrylamide, N-benzyl
methacrylamide, N-(4-methylphenyl)methylmethacrylamide,
N-diphenylmethacrylamide, phthalimidemethyl methacrylamide,
N-(2,2,2-trichloro-1-hydroxy)ethylmethacrylamide,
N-(1,1,3,5-tetramethyl)octylmethacrylamide,
N-(1,5-dimethyl-1-ethyl)hexylmethacrylamide,
N-iso-propylmethacrylamide, N-methylolmethacrylamide,
N-cyclohexylmethacrylamide and
N-(1,1,3-trimethyl)butylmethacrylamide. However, the present
invention is not limited to these monomers.
Examples of the polymerizable unsaturated monomer having a
salt-producing group employable herein include cationic monomers,
anionic monomers, and unsaturated sulfonic acid monomers.
Examples of the cationic monomers among these polymerizable
unsaturated monomers include unsaturated tertiary amine-containing
monomer, and unsaturated ammonium salt-containing monomer. Specific
examples of these cationic monomers include styrenes such as
vinylpyridine, 2-methyl-5-vinylpyridine and
2-ethyl-5-vinylpyridine, styrenes having dialkylamino group such as
N,N-dimethylaminostyrene and N,N-dimethylaminomethylstyrene, esters
having acrylic acid or methacrylic acid dialkylamino group such as
N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl
methacrylate, N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl
methacrylate, N,N-dimethylaminopropyl acrylate,
N,N-dimethylaminopropyl methacrylate, N,N-diethylaminopropyl
acrylate and N,N-diethylaminopropyl methacrylate, vinyl ethers
having dialkylamino group such as 2-dimethylaminoethyl vinyl ether,
acrylamides or methacrylamides having dialkylamino group such as
N-(N,N-dimethylaminoethyl)acrylamide,
N-(N,N-dimethylaminoethyl)methacrylamide,
N-(N,N-diethylaminoethyl)acrylamide,
N,N-(N,N-diethylaminoethyl)methacrylamide,
N-(N,N-dimethylaminopropyl)acrylamide,
N-(N,N-dimethylaminopropyl)methacrylamide,
N-(N,N-diethylaminopropyl)acrylamide and
N-(N,N-diethylaminopropyl)methacrylamide, and those obtained by
quaterizing these monomers with a known quaterizing agent such as
halogenated alkyl (number of carbon atoms in the alkyl moiety: 1 to
18; halogen: chlorine, bromine, iodine), halogenated benzyl such as
benzyl chloride and benzyl bromide, alkylester of alkyl or
arylsulfonic acid such as methanesulfonic acid, benzenesulfonic
acid and toluenesulfonic acid (number of carbon atoms in the alkyl
moiety: 1 to 18) and dialkyl sulfate (number of carbon atoms in the
alkyl moiety: 1 to 4).
Specific examples of the anionic monomers employable herein include
unsaturated carboxylic acid monomer, unsaturated sulfonic acid
monomer, and unsaturated phosphoric acid monomer. Specific examples
of the unsaturated carboxylic acid monomer employable herein
include acrylic acid, methacrylic acid, crotonic acid, itaconic
acid, maleic acid, fumaric acid, citraconic acid,
2-methacryloyloxymethyl succinic acid, and anhydride and salt
thereof.
Specific examples of the unsaturated sulfonic acid monomer
employable herein include styrenesulfonic acid,
2-acrylamide-2-methylpropanesulfonic acid, 3-sulfopropyl
(meth)acrylic acid ester, bis-(3-sulfopropyl)-itaconic acid ester
and salt thereof , and sulfuric acid monoester of
2-hydroxyethyl(meth)acrylic acid and salt thereof.
Specific examples of the unsaturated phosphoric acid monomer
employable herein include vinylphosphonic acid, vinyl phosphate,
bis(methacryloxyethyl)phosphate, diphenyl-2-acryloyloxyethyl
phosphate, diphenyl-2-methacryloyloxyethyl phosphate,
dibutyl-2-acryloyloxyethyl phosphate,
dibutyl-2-methacryloyloxyethyl phosphate, and
dioctyl-2-(meth)acryloyloxyethyl phosphate.
Examples of the monomers copolymerizable with the foregoing
monomers include acrylic acid esters such as methyl acrylate, ethyl
acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate,
n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl
acrylate, n-octyl acrylate, decyl acrylate and dodecyl acrylate,
methacrylic acid esters such as methyl methacrylate, ethyl
methacrylate, isopropyl methacrylate, n-butyl methacrylate,
isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate,
n-hexyl methacrylate, 2-ethylhexylmethacrylate,
n-octylmethacrylate, decyl methacrylate and dodecyl methacrylate,
styrene-based monomers such as styrene, vinyl toluene,
2-methylstyrene and chlorostyrene, and hydroxyl group-containing
acrylates or methacrylates such as 2-hydroxyethyl acrylate,
3-hydroxypropyl acrylate, polyethylene glycol acrylate,
2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate and
polyethylene glycol methacrylate.
Referring to the resin to be used in the process for the
preparation of a pigment dispersion according to the invention, the
preparation of the foregoing vinyl polymer is preferably carried
out by the copolymerization of one or more selected from silicon
macromers represented by the foregoing general formula (III) and
acrylamide or methacrylamide monomers, a polymerizable unsaturated
monomer having a salt-producing group and other monomer components
in a proportion of from 1 to 40% by weight, from 3 to 40% by weight
and from 0 to 89% by weight based on the total amount of monomers,
respectively.
The vinyl polymer to be used in the process for the preparation of
a pigment dispersion according to the invention can be prepared by
the polymerization of the foregoing monomers by a known
polymerization method such as bulk polymerization method, solution
polymerization method, suspension polymerization method and
emulsion polymerization method. Particularly preferred among these
polymerization methods is solution polymerization method.
As the solvent to be used in the solution polymerization method
there is preferably used an organic polar solvent. A water-miscible
organic solvent may be used in admixture with water. Examples of
such an organic solvent include C.sub.1-3 aliphatic alcohols such
as methanol, ethanol and propanol, ketones such as acetone and
methyl ethyl ketone, and esters such as ethyl acetate. Particularly
preferred among these organic solvents are methanol, ethanol,
acetone, methyl ethyl ketone,and mixture there of with water. These
organic solvents may be used singly or in combination of two or
more thereof.
Preferred examples of radical polymerization initiator to be used
in the foregoing polymerization method include azo compounds such
as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl
valeronitrile), 2,2'-azobis(4-methoxy-2,4-dimethyl valeronitrile),
dimethyl-2,2'-azobisbutyrate, 2,2'-azobis(2-methylbutyronitrile)
and 1,1'-azobis(1-cyclohexanecarbonitrile). Other examples of
radical polymerization initiator employable herein include organic
peroxides such as t-butyl peroctoate, dicumyl peroxide,
di-tert-butyl peroxide and dibenzoyl oxide.
These polymerization initiators are used preferably in an amount of
from 0.001 to 2.0 mol %, particularly from 0.01 to 1.0 mol % based
on the amount of monomer mixture.
A polymerization chain transfer agent may be further added during
the foregoing polymerization. Specific examples of the
polymerization chain transfer agent employable herein include
mercaptans such as octyl mercaptan, n-dodecyl mercaptan,
tert-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl
mercaptan and tert-tetradecyl mercaptan, xanthogen disulfides such
as dimethylxanthogen disulfide, diethylxanthogen disulfide and
diisopropylxanthogen disulfide, thiuram disulfides such as
tetramethylthiuram disulfide, tetraethylthiuram disulfide and
tetrabutylthiuram disulfide, halogenated hydrocarbons such as
carbon tetrachloride and ethylene bromide, hydrocarbons such as
pentaphenylethane, acrolein, methacrolein, allyl alcohol,
2-ethylhexyl thioglycolate, terpinolene, .alpha.-terpinene,
.gamma.-terpinene, dipentene, .alpha.-methylstyrene dimer
(preferably having 2,4-diphenyl-4-methyl-1-pentene in an amount of
not lower than 50 parts by weight), unsaturated cyclic hydrocarbon
compounds such as 9,10-dihydroanthracene, 1,4-dihydronaphthalene,
indene and 1,4-cyclohexadiene, and unsaturated heterocyclic
compounds such as xanthene and 2,5-dihydrofurane.
These polymerization chain transfer agents may be used singly or in
combination of two or more thereof.
The polymerization is normally effected at a temperature of from
30.degree. C. to 100.degree. C. (preferably 50.degree. C. to
80.degree. C.) for 1 to 10 hours. The polymerization temperature
and time are properly predetermined depending on the kind of
radical polymerization initiator, monomer and solvent used. The
polymerization is preferably effected in an atmosphere of inert gas
such as nitrogen. After polymerization, copolymers can be isolated
from the reaction solution by any known method such as
reprecipitation method and solvent distillation method. The
copolymer thus obtained can be repeatedly subjected to
reprecipitation or subjected to separation by membrane,
chromatography or extraction so that unreacted monomers are removed
for purification.
Mw of the vinyl polymer of the invention thus obtained is
preferably from not lower than 1,600 to not higher than 50,000
because the resulting printed:image exhibits desired fixability and
gloss and the storage stability and sedimentation properties of the
resulting pigment dispersion and an ink comprising same can be
further improved.
The resin providing dispersibility and/or fixability to be used in
the process for the preparation of a pigment dispersion according
to the invention may be added directly with a surface-treated
pigment, a wetting agent and water and/or added in the form of
aqueous solution or water dispersion at the dispersion step in the
process for the preparation of a pigment dispersion described
later.
The resin providing dispersibility and/or fixability may be added
after the foregoing dispersion step or may be added batchwise at
and after the foregoing dispersion step.
In the case where the vinyl polymer among the foregoing resins is
used in the form of water dispersion, the preparation of such a
water dispersion is preferably accomplished by phase inversion
emulsification method. In other words, such a water dispersion can
be obtained by a process which comprises dissolving the vinyl
polymer thus obtained by polymerization in an organic solvent,
optionally adding a neutralizing agent to the solution thus
obtained to ionize the salt-producing group in the polymer, adding
water to the polymer, and then distilling off the organic solvent
so that the phase of the polymer is inverted to aqueous phase.
The phase inversion emulsification method will be further described
hereinafter.
In some detail, the foregoing vinyl polymer is dissolved in an
organic solvent. In this case, the vinyl polymer is preferably
dissolved in the organic solvent in an amount of from 5 to 50 parts
by weight based on 100 parts by weight of the organic solvent
because a water dispersion having a good stability can be
obtained.
As the organic solvent to be used herein there is preferably used a
hydrophilic organic solvent. Specific examples of the hydrophilic
organic solvent employable herein include alcohol-based solvents,
ketone-based solvents, and ether-based solvents. Examples of the
alcohol-based solvents include methanol, ethanol, n-propanol,
isopropanol, n-butanol, secondary butanol, tertiary butanol,
isobutanol, and diacetone alcohol. Examples of the ketone-based
solvents include acetone, methyl ethyl ketone, diethyl ketone,
dipropyl ketone, methyl isobutyl ketone, and methyl isopropyl
ketone. Examples of the ether-based solvents include diethyl ether,
dibutyl ether, tetrahydrofuran, and dioxane. Preferred among these
hydrophilic organic solvents are isopropanol, acetone, and methyl
ethyl ketone.
The foregoing hydrophilic organic solvents may be used singly or in
admixture of two or more thereof. As necessary, the foregoing
hydrophilic organic solvents may be used in combination with high
boiling hydrophilic organic solvents. Examples of these high
boiling hydrophilic organic solvents include phenoxyethanol,
ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
ethylene glycol monobutyl ether, diethylene glycol monomethyl
ether, diethylene glycol monoethyl ether, diethylene glycol
monobutyl ether, diethylene glycol diethyl ether, and
3-methyl-3-butoxybutanol.
Subsequently, to the foregoing organic solvent solution of vinyl
polymer is added a neutralizing agent as necessary to ionize the
salt-producing group in the vinyl polymer. As the neutralizing
agent there may be used any known acid or base depending on the
kind of the salt-producing group used. Examples of the acid
employable herein include inorganic acid such as hydrochloric acid
and sulfuric acid, and organic acid such as acetic acid, propionic
acid, lactic acid, succinic acid and glycolic acid. Examples of the
base employable herein include tertiary amines such as
trimethylamine and triethylamine, ammonia, sodium hydroxide, and
potassium hydroxide. The present invention is not limited to these
neutralizing agents.
To the organic solvent solution to which the foregoing neutralizing
agent has been added is then added water (particularly
ion-exchanged water or distilled water). The system is then heated
under reduced pressure so that the foregoing organic solvent is
distilled off while distilling off water in a predetermined amount
to obtain a water dispersion of vinyl polymer having a predetermine
solid concentration. The amount of water to be added is preferably
from 100 to 300 parts by weight based on 100 parts by weight of the
organic solvent having the foregoing neutralizing agent added
thereto. In this case, to the foregoing organic solvent may be
added an ordinary dispersant.
The water dispersion of vinyl polymer thus obtained preferably has
a particle diameter of not greater than 300 nm, more preferably not
greater than 200 nm, most preferably not greater than 100 nm. When
the particle diameter of the water dispersion exceeds 300 nm, the
pigment dispersion comprising this water dispersion of vinyl
polymer cannot be provided with desired storage stability
(particularly sedimentation properties).
The amount of the resin providing dispersibility and/or fixability
to be added in the process for the preparation of a pigment
dispersion according to the invention is preferably from not lower
than 1/10 of to not higher than three times the amount of the
surface-treated pigment by weight. When the added amount of the
resin falls below the above defined range, the desired effect of
providing dispersibility and/or fixability cannot be exerted. As a
result, the resulting pigment dispersion cannot be provided with
desired storage stability (particularly sedimentation properties)
Further, images printed with an ink comprising this pigment
dispersion cannot be provided with desired fixability or gloss. On
the contrary, when the added amount of the resin exceeds the above
defined range, an ink having a desired print density prepared from
this pigment dispersion exhibits a high viscosity that occasionally
makes it impossible for itself to be ejected from the ink jet
head.
In order to dissolve and/or disperse the foregoing resin providing
dispersibility and/or fixability in the pigment dispersion or ink
more stably, an additive which forms a salt with the resin can be
added. Specific preferred examples of these additives include
aminomethyl propanol, 2-aminoisopropanol, monoethanolamine,
diethanolamine, triethanolamine, tri-iso-propanolamine, morpholine,
and ammonia. The amount of these additives to be added may be not
lower than the neutralization equivalent of the foregoing resin
providing dispersibility and/or fixability.
In addition to the foregoing additives, as a dissolution aid for
the alkali-soluble resin which is used as a resin providing
dispersibility and/or fixability there may be used propylene
glycol, 2-propanol or the like.
Pigment Dispersion
In the process for the preparation of a pigment dispersion
according to the invention, the foregoing wetting agents may be
used singly or in combination of two or more thereof. The amount of
the wetting agent to be added is not specifically limited so far as
the addition of the wetting agent at least exerts an effect of
enhancing the efficiency of dispersion and doesn't affect the
dispersion of the pigment and the actual use of the pigment
dispersion. In practice, however, the amount of the wetting agent
to be added is preferably from 0.05 to 50% by weight, more
preferably from 0.1 to 30% by weight based on the weight of the
pigment dispersion at the dispersion step. When the added amount of
the wetting agent falls below 0.05% by weight, the resulting
wetting effect is not sufficient. On the contrary, when the added
amount of the wetting agent exceeds 50% by weight, the dispersion
of the particulate pigment can be unstable.
The foregoing resins providing dispersibility and/or fixability may
be used singly or in combination of two or more thereof. The amount
of these resins to be added is preferably from not lower than 1/10
of to not higher than three times the amount of the pigment as
previously mentioned.
Process for the Preparation of Pigment Dispersion
The process for the preparation of a pigment dispersion according
to the invention will be further described hereinafter.
The process for the preparation of a pigment dispersion according
to the invention mainly comprises a "step of subjecting a pigment
to surface treatment" and a "step of dispersing a surface-treated
pigment".
The "step of subjecting a pigment to surface treatment" comprises
mixing a pigment and an agent for surface treatment or heating such
a mixture in an aqueous or non-aqueous solvent to effect surface
treatment of the pigment (introduction of dispersibility-providing
group). After surface treatment, the resulting reaction product can
be repeatedly subjected to rinsing, ultrafiltration, reverse
osmosis, centrifugal separation and/or filtration to remove
residual unreacted materials, by-products, residual treatment, etc.
there from. Thus, a surface-treated pigment can be obtained.
The pigment to be used at the surface treatment step has previously
been finely ground before being provided with a hydrophilic
dispersibility-providing group. The grinding of the pigment can be
carried out in a wet or dry manner using a grinding medium such as
zirconia beads, glass beads and inorganic salts. Examples of the
grinding apparatus to be used herein include attritor, ball mill,
and oscillation mill. The pigment thus ground is preferably
subjected to rinsing, filtration or the like so that contaminants
produced from the grinding medium or grinding apparatus are
removed.
In particular, since a grinding method using dry grinding and an
inorganic salt in combination (salt milling) causes the grinding
medium to produce a contaminant which is a water-soluble inorganic
salt, rinsing with water can be used to remove the contaminant
easily.
The "step of dispersing a surface-treated pigment" comprises adding
the surface-treated pigment obtained at the foregoing "step of
subjecting a pigment to surface treatment", optionally in the form
of slurry, wet cake or the like, to an aqueous medium (particularly
ion-exchanged water or distilled water) (with a wetting agent and
optionally a neutralizing agent, etc.) in an amount such that the
pigment concentration is from about 5 to 50% by weight (by weight).
The wetting agent may be mixed with at least the pigment at the
dispersion step. The addition of the wetting agent may be effected
before or during the dispersion step.
Subsequently, the mixture is given a proper shearing force by an
agitator or dispersing apparatus so that the particulate pigment is
dispersed in an aqueous medium to obtain a surface-treated pigment
dispersion.
The dispersion step further comprises the addition of the foregoing
resin providing dispersibility and/or fixability. The foregoing
resin may be added during or after the dispersion step or may be
added batchwise during and after the dispersion step. The time of
addition of the fore going resin may be properly selected depending
on the kind of the resin used and the properties of the pigment
dispersion thus obtained and the ink comprising same.
The foregoing "step of subjecting a pigment to surface treatment"
and "step of dispersing a surface-treated pigment" can be
continuously effected. In particular, when the surface treatment of
the pigment is effected in an aqueous solvent, the reaction solvent
to be used at the surface treatment step and the dispersing medium
to be used at the dispersion step can be aqueous altogether, making
it easy to arrange a continuous procedure. However, the removal of
residual unreacted materials and by-products produced at the
surface treatment step is preferably effected before the dispersion
step, making it easy to eventually obtain a pigment dispersion
having abetter dispersion stability. On the other hand, in some
cases, the solvent to be used at the surface treatment step is
preferably non-aqueous to make it easy to separate and remove
residual unreacted materials, etc. from the desired surface-treated
pigment.
The process for the preparation of a pigment dispersion according
to the invention will be further described herein after with
reference to a process for the preparation of a pigment dispersion
having a sulfur-containing dispersibility-providing group on the
surface thereof by way of example.
At the "step of subjecting a pigment to surface treatment", a
finely divided or powdered pigment is put in an aprotic solvent
(e.g., N-methyl-2-pyrrolidone or sulfolane) in an amount of from 3
to 200 times by weight that of the pigment. The pigment is then
treated with a sulfonating agent while being arranged for particle
diameter. Examples of the sulfonating agent employable herein
include sulfonated pyridine, sulfamic acid, amidesulfuric acid,
fluorosulfuric acid, chlorosulfuric acid, sulfur trioxide, fumic
sulfuric acid, and sulfuric acid. These sulfonating agents may be
used singly or in combination of two or more thereof. The treatment
with such a sulfonating agent may be effected under heating (about
60.degree. C. to 200.degree. C.) or with stirring. The heating may
be effected before or after the addition of the sulfonating
agent.
After the sulfonation, the resulting pigment slurry is freed of the
aprotic solvent and residual sulfonating agent. The removal of
these residual materials can be accomplished by repeatedly
subjecting the pigment slurry to rinsing, ultrafiltration, reverse
osmosis, centrifugal separation, and/or filtration. The
contaminants which have entered in the pigment slurry at the
foregoing uniformalization/dispersion step and sulfonation step are
removed together with the aprotic solvent and sulfonating
agent.
Subsequently, at the "step of dispersing a surface-treated
pigment", the sulfonated pigment obtained at the foregoing "step of
subjecting a pigment to surface treatment" is added to an aqueous
medium (particularly ion-exchanged water or distilled water)
together with the foregoing wetting agent and neutralizing agent in
an amount such that the pigment concentration is from 5 to 50% by
weight (as calculated in terms of weight). If necessary, a resin
providing dispersibility and/or fixability can be further added to
reduce the required dispersion time, thereby obtaining an aqueous
dispersion of pigment.
Examples of the apparatus which can be used in dispersion include
stirrer, paint shaker, ball mill, sand mill, roll mill, speed line
mill, homomixer, ultrasonic homogenizer, nanomizer, and
microfluidizer.
As the wetting agent there may be used any of the foregoing various
wetting agents. Particularly preferred examples of the wetting
agent employable herein include acetylene glycols, acetylene
alcohols, glycol ethers, and alkylene glycols as previously
mentioned.
As the resin providing dispersibility and/or fixability there may
be used any of the foregoing various resins. Particularly preferred
examples of the resin employable herein include alkali-soluble
resin, and water-soluble or water-dispersible vinyl polymer as
previously mentioned.
The neutralizing agent is added to dissociate the sulfur-containing
dispersibility-providing group on the surface of the pigment and/or
the foregoing resin salt-forming group. Specific examples of the
neutralizing agent employable herein include sodium hydroxide,
lithium hydroxide, potassium hydroxide, ammonium hydroxide,
triethanolamine, tri-iso-propanolamine, diethanolamine,
monoethanolamine, and 2-amino-2-methyl-1-propanol.
The amount of the dispersibility-providing group to be introduced
onto the surface-treated pigment of the invention is preferably not
lower than 10.times.10.sup.-6 equivalent, more preferably not lower
than 15.times.10.sup.-6 equivalent per g of particulate pigment.
When the amount of the dispersibility-providing group to be
introduced falls below 5.times.10.sup.-6 equivalent per g of
particulate pigment, the dispersed pigment particles undergo
agglomeration, occasionally causing the deterioration of stability
of pigment dispersion such as thickening of dispersion and increase
of diameter of dispersed pigment particles. However, when the
stability of the pigment dispersion is as desired because of the
foregoing resin providing dispersibility and/or fixability, the
amount of the dispersibility-providing group to be introduced is
not limited to the above defined range.
The measurement of the introduced amount of the foregoing
dispersibility-providing group, if it is a sulfur-containing
dispersibility-providing group, can be accomplished by subjecting
an aqueous dispersion of pigment to oxygen flask combustion,
allowing the aqueous dispersion to be absorbed by an aqueous
solution of hydrogen peroxide, determining the amount of sulfuric
acid ion (divalent) by ion chromatography, and then converting the
measurements in terms of sulfonic acid group and sulfinic
group.
The zeta potential of the pigment dispersion of the invention is
preferably such that the absolute value of the zeta potential of
particulate pigment measured at a temperature of 20.degree. C. and
pH of from 8 to 9 in the form of diluted solution obtained by
diluting the pigment dispersion with ion-exchanged water to an
extent such that the pigment concentration is from 0.001 to 0.01%
by weight is not lower than 30 mV, more preferably not lower than
40 mV, even more preferably not lower than 50 mV. When the absolute
value of zeta potential of particulate pigment in the pigment
dispersion is not higher than 20 mV, the storage stability of the
pigment dispersion is deteriorated as in the case where the
introduced amount of the dispersibility-providing group is
insufficient.
The surface tension at 20.degree. C. of the pigment dispersion at
least during the dispersion step in the preparation process of the
invention is preferably not higher than 40 mN/m. When the surface
tension of the pigment dispersion at the dispersion step exceeds 40
mN/m, it is made difficult to effect efficient dispersion,
occasionally resulting in the entrance of a large amount of metal
ions and contaminants such as peelings from particulate pigment
into the pigment dispersion. In general, the surface tension of the
dispersion of surface-treated pigment is as high as the same as
that of water (70 to 72 mN/m). Accordingly, the addition of the
foregoing proper wetting agent is required.
The total amount of polyvalent metal ions contained in the liquid
component of the pigment dispersion prepared by the preparation
process of the invention is preferably not higher than 600 ppm.
Further, the amount of Si, Ca, Mg, Fe, Cr and Ni ions contained in
the liquid component each are preferably not higher than 100
ppm.
By thus suppressing the amount of polyvalent metal ions and Si, Ca,
Mg, Fe, Cr and Ni ions to be contained in the liquid component of
the pigment dispersion to not higher than the foregoing
predetermined level, the pigment dispersion can maintain the
desired storage stability (particularly sedimentation properties)
over an extended period of time. The ink comprising this pigment
dispersion exhibits excellent ink properties (particularly storage
stability such as sedimentation properties) and provides an ink jet
recording ink having excellent printing properties (particularly
ejection stability).
The average diameter of the surface-treated pigment particles in
the pigment dispersion obtained by the preparation process of the
invention is preferably from 10 to 300 nm. When the average
particle diameter of the surface-treated pigment is les than 10 nm,
light fastness of the pigment is extremely deteriorated. On the
other hand, when the average particle diameter exceeds 300 nm, the
effect of spontaneous sedimentation becomes particularly
remarkable, causing the pigment concentration to be distributed in
the dispersed system. From the standpoint of sedimentation
properties, the average diameter of the particulate pigment is
preferably not greater than 200 nm, more preferably not greater
than 130 nm, most preferably not greater than 100 nm.
Ink Jet Recording Ink
The ink jet recording ink comprising the pigment dispersion of the
invention will be described hereinafter.
The ink according to the invention comprises at least the foregoing
pigment dispersion prepared by the process for the preparation of
pigment according to the invention. The content of the pigment
dispersion is preferably from 0.5 to 30% by weight, more preferably
from 1.0 to 12% by weight, most preferably from 2 to 10% by weight
as calculated in terms of weight concentration of surface-treated
pigment. When the content of pigment in the ink falls below 0.5% by
weight, the resulting print density may be insufficient. On the
contrary, when the content of pigment in the ink exceeds 30% by
weight, the amount of ink additives such as humectant components to
be incorporated in the ink is limited from the standpoint of ink
viscosity, causing the nozzle of the ink jet head to be clogged or
increasing the ink viscosity. Thus, the desired ejection stability
cannot be obtained.
Referring to the ink of the invention, when the pigment
concentration falls within the above defined range, the pigment
dispersion of the invention can be used as such as an ink. If
necessary, the ink of the invention can comprise the following
various additives incorporated therein.
The ink to be used in the invention may comprise a penetrating
agent incorporated therein for the purpose of enhancing its
penetrating power with respect to the recording medium on which an
image is formed. The penetrating agent to be used herein may be the
same or different from the foregoing wetting agent to be added at
the foregoing dispersion step. A wetting agent which makes the
pigment particles to come in contact with each other more during
dispersion and enhances the penetrating power of the ink with
respect to the recording medium during printing can be previously
selected to secure both the properties.
Further, in the case where the ink of the invention is used for ink
jet printer, the wetting agent to be used herein preferably can be
little bubbled and can be difficultly dried in the nozzle of the
ink jet head. The use of a compound which satisfies all these
properties as a wetting agent makes it possible to eliminate the
necessity of adding a wetting agent and a penetrating agent
individually and thus is advantageous from the standpoint of ink
properties, particularly viscosity. Examples of compounds which
satisfy the requirements of wetting agent and penetrating agent
include acetylene glycols, acetylene alcohols, glycol ethers, and
alkylene glycols as mentioned above.
Specific examples of the acetylene glycols or acetylene alcohols
include compounds represented by the following general formula (I)
or (II): ##STR5##
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently
represent an alkyl group; and the sum of m.sub.1 and n.sub.1 is
from 0 to 30. ##STR6##
wherein R.sup.5 and R.sup.6 each independently represent an alkyl
group; and m.sub.2 is from 0 to 30.
Specific examples of trade name of these compounds include Surfynol
TG, Surfynol 104, Surfynol 420, Surfynol 440, Surfynol 465,
Surfynol 485, Surfynol 61, Surfynol 82 (produced by Air Products
Inc.), and Acetylenol E-H, Acetylenol E-L, and Acetylenol E-O
(produced by Kawaken Fine Chemicals Co., Ltd.).
Specific examples of glycol ethers employable herein include
diethylene glycol mono-n-butyl ether, triethylene glycol
mono-n-butyl ether, propylene glycol mono-n-butyl ether, and
dipropylene glycol mono-n-butyl ether. Further specific examples of
these glycol ethers include the foregoing other glycol ethers.
When the foregoing wetting agent and penetrating agent are used,
the solubility of the foregoing resin providing dispersibility
and/or fixability, particularly an alkali-soluble resin, in the
dispersion and ink can be improved, making it possible to fairly
maintain the storage stability of the dispersion and ink. Further,
the fixability and gloss of the image printed with the ink
comprising these additives can be improved. Moreover, a high
quality image having little feathering and bleeding can be
obtained.
The ink of the invention may comprise as a penetrating agent the
foregoing acetylene glycols, acetylene alcohols, glycol ethers and
alkylene glycols incorporated therein, singly or in combination.
The amount of these penetrating agents to be incorporated is
preferably from 0 to 30% by weight, more preferably from 0.5 to 10%
by weight. When the amount of these penetrating agents to be
incorporated exceeds 30% by weight, the ink unevenly wets around
the nozzle of the ink ejection head, making it difficult for the
ink to be ejected in a stable manner.
Other examples of compounds which can be used as penetrating agents
for the ink of the invention include the foregoing alcohols,
nonionic surface active agents, water-soluble organic solvents, and
other surface active agents.
The ink to be used in the invention may comprise these penetrating
agents incorporated therein singly or in combination of two or more
thereof.
The ink to be used in the invention may comprise as auxiliary agent
for the foregoing penetrating agent the foregoing or other surface
active agents and hydrophilic high boiling low volatility solvents
such as high boiling low volatility polyhydric alcohols and
monoetherification, dietherification or esterification product
thereof incorporated therein singly or in combination of two or
more thereof for the purpose of controlling the penetrating power
of the ink and improving the resistance to nozzle clogging, the
moisture retention of the ink and the solubility of the penetrating
agent.
Examples of the high boiling low volatility polyhydric alcohols
employable herein include glycerin, ethylene glycol, diethylene
glycol, triethylene glycol, propylene glycol, dipropylene glycol,
hexylene glycol, polyethylene glycol, polypropylene glycol,
1,5-pentanediol, and 1,2-hexanediol. Further examples of the high
boiling low volatility polyhydric alcohols include
monoetherification, dietherification and esterification products of
these compounds.
Other examples of the high boiling low volatility polyhydric
alcohols include hydrophilic high boiling low volatility solvents
such as nitrogen-containing organic solvent, e.g.,
N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone,
monoethanolamine, N,N-dimethylethanolamine,
N,N-diethylethanolamine, diethanolamine, N-n-butyldiethanolamine,
tri-iso-propanolamine, triethanolamine.
The ink to be used in the invention may further comprise a small
amount of a high volatility monohydric alcohol such as ethanol,
propanol, isopropanol and butanol incorporated therein in addition
to water as a main solvent for the purpose of improving the
dryability thereof.
The ink to be used in the invention may further comprise a pH
buffer incorporated therein to adjust the pH value thereof to an
optimum value. Examples of the ph buffer employable herein include
potassium biphthalate, potassium dihydrogenphosphate, sodium
dihydrogenphosphate, sodium tetraborate, potassium
hydrogentartrate, sodium hydrogencarbonate, sodium carbonate, tris
(hydroxymethyl) aminomethane, and tris (hydroxymethyl) aminomethane
hydrochloride. The content of the pH buffer is preferably such that
the pH value of the ink is from about 7 to 10 from the standpoint
of the durability of the head member and the stability of the
ink.
Further, the pigment dispersion of the invention and the ink
comprising same may comprise as other additives such as
mildewproofing agent, preservative and rust preventive benzoic
acid, dichlorophene, hexachlorophene, sorbic acid, p-hydroxybenzoic
acid ester, ethylenediaminetetraacetic acid (EDTA), sodium
dehydroacetate, 1,2-benzothiazoline-3-one, 3,4-isothiazoline-3-one,
oxazoline compound, alkylisothiazolone, chloroalkylisothiazolone,
benzisothiazolone, bromonitroalcohol and/or chloroxylenol
incorporated therein as necessary.
Moreover, the pigment dispersion of the invention and the ink
comprising same may comprise urea, thiourea and/or ethylene urea
incorporated therein for the purpose of inhibiting the drying of
the nozzle.
The ink of the invention may further comprise a resin providing
dispersibility and/or fixability incorporated therein as necessary.
As such a resin there may be used one previously mentioned.
The properties of the ink to be used in the invention can be
properly controlled. In accordance with a preferred embodiment of
implication of the present invention, the viscosity of the ink is
preferably not higher than 10 mPa.multidot.sec (20.degree. C.),
more preferably not higher than 5 mPa.multidot.sec (20.degree. C.).
The ink having a viscosity falling within the above defined range
can be ejected from the ink ejection head in a stable manner.
The surface tension of the ink can be properly controlled. In
practice, however, the surface tension of the ink is preferably
from 25 to 50 mN/m (20.degree. C.), more preferably from 30 to 40
mN/m (20.degree. C.).
Action
In the course of development of the pigment dispersion of the
invention and the process for the preparation thereof, the
inventors obtained the following knowledge. However, the present
invention is not limited to the following inference.
As previously mentioned, with the enhancement of the quality of
image printed by the ink jet printer and the operation speed of the
ink jet printer, it has lately been made difficult to secure stable
ejection properties particularly with a pigment ink. An ink
comprising a self-dispersible surface-treated pigment doesn't need
to comprise as a dispersant a resin or the like incorporated
therein. Therefore, the deterioration of storage stability (e.g.,
deterioration of sedimentation properties by agglomeration of
pigment particles in particular) caused by separation of dispersed
pigment from the pigment doesn't occur. Accordingly, it has been
thought that no malejection or deterioration of storage stability
occurs.
However, even a surface-treated pigment ink is subject to deflected
flying of ink dot when subjected to printing by an ink jet printer
which has a reduced nozzle diameter and a raised head driving
frequency to provide a high image quality and a high operation
speed. Further, when printing is resumed after prolonged suspension
of printing, the pigment particles undergo agglomeration that
causes the nozzle to be clogged, resulting in frequent occurrence
of malejection.
From the standpoint of properties, the surface-treated pigment has
little or no fixing components with respect to the recording medium
and glossy components provided on the surface of the particulate
pigment. Accordingly, when printed on a glossymedium (e.g.,
glossypaper, glossy film) requiring print quality which is equal to
or higher than that of photograph, the surface-treated pigment can
provide an image having an insufficient fixability or gloss, making
it impossible to obtain satisfactory print quality.
Under the circumstances, the inventors found that when the
dispersion of a surface-treated pigment in an aqueous medium in the
process for the preparation of a dispersion containing a
self-dispersible surface-treated pigment is effected in a short
period of time in the presence of a proper wetting agent and
optionally a specific resin which have been previously added, the
foregoing problems such as malejection and agglomeration of pigment
particles can be solved. It was also found that images printed with
this dispersion exhibit desired fixability and gloss. This effect
can be inferred as follows.
The surface-treated pigment acts to introduce a hydrophilic
dispersibility-providing group onto the surface of finely divided
pigment particles. It is necessary at the surface treatment step
that by-products and residual materials produced during the
reaction be removed. The resulting pigment is in concentrated form
such as slurry, wet cake and dried material. The uniform dispersion
of the concentrated surface-treated pigment particles in an aqueous
solvent is effected at the subsequent dispersion step.
The term "step of dispersing a surface-treated pigment" as used
herein differs from the dispersion of dispersant type pigment
particles using a conventional resin dispersant or the like. In the
conventional dispersant type pigment dispersion, it is necessary
that a pigment, a dispersant and water be dispersed while being
given a high shearing force by a dispersing apparatus. This is
because this type of dispersion requires that the agglomerate of
pigment particles be dispersed in an aqueous solvent with a
dispersant adsorbed to the surface thereof while being ground
(finely divided).
On the other hand, the step of dispersing a surface-treated pigment
is subject to a trouble that when a particulate pigment is
dispersed in a high concentration while being given a high shearing
force, the pigment particles can be agglomerated to increase its
particle diameter. This is presumably because the pigment is given
a high shearing force that causes physical separation of
hydrophilic group from the surface of the pigment or destroys the
pigment particles to smaller particles having unhydrophilicized
faces.
The agglomeration caused by giving a high shearing force was more
remarkably confirmed with organic pigments than with carbon black
pigments. Further, if the pigment has a polymer material introduced
onto (chemically bonded to) the surface thereof, it is more likely
that the polymer material can be physically separated from the
surface of the pigment because its molecular weight is higher than
that of the hydrophilic dispersibility-providing group. It was
found that this problem can be somewhat solved by adding the
foregoing resin providing dispersibility and/or fixability,
particularly a resin providing dispersibility, at the dispersion
step. This is presumably because such a resin is adsorbed to the
surface of the particulate pigment from which a hydrophilic
dispersible group has been separated or having unhyrophilicized
faces exposed to act as a dispersant. As a result, in this case,
improvement of properties (particularly dispersion stability) were
recognized as compared with the conventional dispersible pigment.
However, the foregoing properties of surface-treated pigment
couldn't maintained and improved.
The inventors then tried to disperse pigment particles with a
shearing force which is so low that the pigment particles cannot be
destroyed for a longer period of time. The time required until the
pigment was finely divided to a diameter of about 100 nm was as
long as not shorter than 10 hours.
Thus, when dispersion was effected under mild shearing conditions
for a longer period of time, the agglomeration of pigment particles
or increase of particle diameter thereof caused by the destruction
of pigment particles didn't occur. However, a large amount of
contaminants (Si, Fe, Ni, Cr ions) produced from the dispersing
medium enter into the pigment dispersion and ink, adversely
affecting the long time storage stability of the pigment dispersion
and ink and the ejectability of the ink.
For example, when glass beads are used, the resulting friction
causes Si, which is a main component thereof, to be dissolved in
the ink. It was confirmed that when an ink having Si dissolved
therein is used with an ink jet printer, Si dissolved in the ink is
solidified and attached to the area in the vicinity of the nozzle,
causing the occurrence of deflected flying or malejection.
On the other hand, when a dispersing medium having a high hardness
such as zirconia beads is used to prevent friction of these media,
the inner wall of the dispersing apparatus (made of stainless
steel, for example) is abraded to cause Fe, Ni, Cr, etc., which are
constituents thereof, to enter into the dispersion and ink,
resulting in the occurrence of malejection and change of physical
properties after prolonged storage similarly to the foregoing
case.
The reason why the storage stability and stability in ejection of
ink are impaired by the contaminants such as metal ion mixed in the
pigment dispersion and ink comprising same is not made clear.
However, taking into account the fact that the surface-treated
pigment can maintain its dispersion stability by the electrical
repulsion of dispersible groups provided on the surface thereof,
this is presumably because the effect of metal ions impairs the
electrical repulsion to cause the agglomeration of pigment
particles.
Accordingly, it was thought necessary that dispersion be effected
with a mild shearing force for minimized period of time to solve
the problems such as agglomeration of pigment particles, increase
of particle diameter thereof, malejection and deterioration of
storage stability.
The inventors made studies of solution to these problems. As a
result, it was found that the addition of a proper wetting agent
makes it possible to drastically reduce the dispersion time (to
about one tenth). As a result, it was found that a pigment ink for
ink jet printer can be prepared satisfying both stabilized printing
properties and storage stability free from change of physical
properties in an ink jet printer having a head which has a reduced
nozzle diameter and is driven at a high frequency for the late
demand for enhancement of image quality and operation speed.
However, as previously mentioned, from the standpoint of
properties, the surface-treated pigment has little or no fixing
components with respect to the recording medium and glossy
components provided on the surface of the particulate pigment.
Accordingly, when printed on a glossymedium (e.g., glossypaper,
glossy flim) requiring print quality which is equal to or higher
than that of photograph, the surface-treated pigment can provide an
image having an insufficient fixability or gloss, making it
impossible to obtain satisfactory print quality. The demand for the
enhancement of the print quality of the surface-treated pigment to
equal to or higher than that of photograph has been growing rapidly
in recent years.
Most inks for ink jet recording which has heretofore been used are
dye inks comprising a water-soluble dye as a colorant and attain
satisfactory level in the fixability and gloss on a glossy
medium.
However, these inks comprise a water-soluble dye as a colorant and
thus are disadvantageous in that they are inferior to those
comprising a pigment in durability such as water fastness and light
fastness. The inventors thought that these disadvantages can be
solved by the use of a pigment ink, particularly a self-dispersible
surface-treated pigment ink which is most excellent in properties
required for ink jet recording among pigment inks.
The inventors then made extensive studies. As a result, the
inventors successfully prepared a pigment ink for ink jet printer
which satisfies both the foregoing printing properties and storage
stability of surface-treated pigment ink and provides a printed
image having desired fixability and gloss on a glossy medium by
adding a resin providing dispersibility and/or fixability in
combination with a proper wetting agent at and/or after a
dispersion step. The present invention has thus been worked
out.
Examples of materials which can be extremely effectively used as a
wetting agent among materials essential for the pigment dispersion
having the foregoing properties and ink comprising same include
acetylene glycols and acetylene alcohols represented by the
following general formulae (I) and (II): ##STR7##
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently
represent an alkyl group; and the sum of m.sub.1 and n.sub.1 is
from 0 to 30. ##STR8##
wherein R.sup.5 and R.sup.6 each independently represent an alkyl
group; and m.sub.2 is from 0 to 30.
These acetylene glycols and acetylene alcohols further have a high
effect as penetrating agent and have properties for inhibiting
bubbling. From this standpoint of view, too, these acetylene
glycols and acetylene alcohols are useful as wetting agent and
penetrating agent during dispersion. The use of these acetylene
glycols and acetylene alcohols during the preparation of the
pigment dispersion makes it possible to eliminate the necessity of
further adding a wetting agent or penetrating agent or a material
having both the two properties individually or during the
preparation of ink and hence reduce the ink viscosity to
advantage.
Examples of materials which can be particularly effectively used as
resin providing dispersibility and/or fixability among the
materials essential for the pigment dispersion having the foregoing
properties and ink comprising same include alkali-soluble resin,
and vinyl polymer obtained by the copolymerization of one or more
selected from the group consisting of silicon macromer represented
by the following general formula (III) and acrylamide or
methacrylamide-based monomer (excluding base-producing groups), a
polymerizable unsaturated monomer having a salt-producing group and
a monomer copolymerizable with these monomers in the presence of a
radical polymerization initiator:
wherein X represents a polymerizable unsaturated group; Y
represents a divalent connecting group; R represents a hydrogen
atom, lower alkyl group, aryl group or alkoxy group, with the
proviso that a plurality of R's may be the same or different;
Z represents a monovalent siloxane polymer moiety having a
number-average molecular weight of at least about 500; v represents
0 or 1; and w represents an integer of from 1 to 3.
The use of the foregoing alkali-soluble resin or specific vinyl
polymer as a resin makes it possible to obtain fixability and
glass, which is originally possessed by the surface-treated
pigment, and hence provide good print quality and durability on a
glossy medium requiring these properties. It was also found that
since these resins also act as dispersing agent, the resulting
pigment dispersion and ink comprising same exert a drastic effect,
i.e., exhibit further improvement of storage stability
(particularly sedimentation properties).
It was further found that printing with an ink comprising the
foregoing surface-treated pigment, wetting agent/penetrating agent
and specific resin makes it possible to realize a printed image
having little feathering and bleeding and excellent in fixability
and gloss regardless of the kind of the recording medium used.
The reason for this effect is not yet made clear but can be
inferred.
In other words, the self-dispersible surface-treated particulate
pigment undergoes ionic dissociation of dispersibility-providing
group in an ink to produce an electrical repulsion between the
particles and thus can be dispersed in the ink in a stable
manner.
Then, when the ink is attached to the recording medium, ionic
materials (e.g., alkaline earth metal ions such as magnesium and
calcium ions) in the recording medium are eluted with the ink.
Thus, the foregoing dispersibility-providing group (particularly
sulfinic acid group or sulfonic acid group as a sulfur-containing
dispersibility-providing group) and the foregoing ionic materials
undergo salting-out reaction to bond to each other, causing the
agglomeration of pigment particles and hence the separation of the
pigment particles from the liquid component in the ink. As a
result, the agglomerate of pigment is precipitated on and adsorbed
to the surface of the recording medium. Thereafter, the liquid
component penetrates and diffuses into the surface and interior of
the recording medium. This is presumably why a printed image having
little feathering and bleeding can be obtained.
Further, the water fastness of the printed matter thus obtained is
close to that of sulfate in terms of difficulty in dissolution in
water. Thus, the printed matter exhibits a higher water fastness
than that printed with the dispersible pigment ink which has
heretofore been used.
The resin to be incorporated in the ink of the invention
(particularly alkali-soluble resin or specific vinyl polymer)
exhibits a good affinity for the foregoing wetting
agent/penetrating agent and thus undergoes no
agglomeration/precipitation in the ink. Thus, the resin can be
dissolved or dispersed in the ink in a stable manner. The foregoing
resin also has a hydrophobic moiety and a hydrophilic moiety in its
molecular structure. Thus, the foregoing resin acts to be adsorbed
to the surface of the particulate pigment at its hydrophobic
moiety. When this ink is attached to the recording medium, the
foregoing resin is adsorbed to the surface of the agglomerate of
pigment as the pigment particles undergo agglomeration and
sedimentation. The liquid component thus separated penetrates and
diffuses into the recording medium. When the resin is adsorbed to
the surface of the agglomerate of pigment, agglomerated pigment
particles are strongly bonded to each other with the resin
interposed therebetween. Further, since the foregoing wetting
agent/penetrating agent in the liquid component penetrates and
diffuses into the recording medium together with a part of the
resin, the agglomerate of pigment is strongly bonded to the
recording medium with the interposition of the resin. This is
presumably why the resulting image is excellent in fixability.
Further, the resin is adsorbed to the surface of the agglomerate of
pigment to develop the smoothness of the image. This is presumably
why an image with an excellent gloss can be realized.
Moreover, the surface-treated particulate pigment to be
incorporated in the ink of the invention can prevent the
dispersibility-providing group from being separated from the
surface thereof and thus is excellent in dispersion stability.
Therefore, the foregoing wetting agent/penetrating agent, which has
heretofore been limited in its amount to be added to the
conventional dispersible pigment to maintain its dispersion
stability, can be added in an amount such that the desired
penetrating power can be realized. Accordingly, in full-color
printing in particular, the ink of the invention undergoes little
feathering and bleeding even at an image area where two or more
color inks are imposed on each other and come in contact with each
other, making it possible to obtain a sharp image.
EXAMPLES
The present invention will be further described in the following
examples, but the present invention should not be construed as
being limited to the following Examples 1 to 23. (The term
"surface-treated pigment" as used in the following examples and
comparative examples is meant to indicate a "self-dispersible
pigment which has a hydrophilic dispersibility-providing group
chemically bonded to the surface of a particulate pigment directly
and/or with the interposition of a polyvalent group to make itself
dispersible in water". The term "parts and %" as used in the
following examples and comparative examples are by weight unless
otherwise specified.) For the measurement of the physical
properties (surface tension, average particle diameter) of the
pigment dispersions obtained in the following Examples 1 to 21 and
Comparative Examples 1 to 3, the following methods were
employed.
"Measurement of Surface Tension"
The pigment dispersions obtained in the various examples and
comparative examples were measured for surface tension at
20.degree. C. by means of a Type CBVP-A3 surface tension balance
(produced by Kyowa Interface Science Co., Ltd.).
"Measurement of Average Particle Diameter"
The pigment dispersions obtained in the various examples and
comparative examples were each diluted with ion-exchanged water
such that the pigment concentration was from 0.001 to 0.01% by
weight (because there is some difference in optimum concentration
during measurement between pigments). The dispersed particles were
then measured for average particle diameter at 20.degree. C. by
means of a Type ELS-800 particle size distribution meter (produced
by OTSUKA ELECTRONICS CO., LTD).
Examples of the synthesis of a "resin providing dispersibility
and/or fixability" which is an essential compounding material for
the pigment dispersion of the invention will be given below. "Vinyl
Polymer 1" prepared in Synthesis Example 1 below was then used in
the following Examples 6, 14, 17 and 20. On the other hand, "Vinyl
Polymer 2" prepared in Synthesis Example 2 was then used in the
following Examples 9, 12 and 18.
Synthesis Example 1
(1) Synthesis of "Vinyl Polymer 1"
Into a reaction vessel equipped with an agitator, a reflux
condenser, a dropping funnel, a thermometer and a nitrogen inlet
pipe were charged 20 parts of methyl ethyl ketone as a
polymerization solvent and 12 parts of tert-butyl methacrylate, 2
parts of polyethylene glycol methacrylate, 5 parts of acrylic acid,
1 part of a silicon macromer FM-0711 (trade name, produced by
CHISSO CORPORATION) and 0.6 part of n-dodecyl mercaptan as
polymerizable unsaturated monomers. The air within the reaction
vessel was then thoroughly replaced by nitrogen gas. Separately,
into the dropping funnel in which the air within had been
thoroughly replaced by nitrogen gas were charged 48 parts of
tert-butyl methacrylate, 8 parts of polyethylene glycol
methacrylate, 20 parts of acrylic acid, 4 parts of a silicon
macromer FM-0711 (trade name, produced by CHISSO CORPORATION), 2.4
parts of n-dodecyl mercaptan, 60 parts of methyl ethyl ketone, and
0.2 part of 2,2'-azobis(2,4-dimethylvaleronitrile).
In a nitrogen atmosphere, the mixture in the reaction vessel was
then heated to a temperature of 65.degree. C. with stirring. At
this temperature, the mixture in the dropping funnel was then
gradually added dropwise to the mixture in the reaction vessel in 3
hours. When 2 hours passed after the termination of dropwise
addition, to the mixture was then added a solution of 0.1 part of
2,2'-azobis(2,4-dimethylvaleronitrile) in 5 parts of methyl ethyl
ketone. The mixture was then subjected to ripening at a temperature
of 65.degree. C. for 2 hours and at a temperature of 70.degree. C.
for 2 hours to obtain "Vinyl Polymer 1".
(2) Measurement of Weight-Average Molecular Weight, Glass
Transition Temperature (Tg) and Acid Value (AV) of "Vinyl Polymer
1".
The solution of "Vinyl Polymer 1" obtained in Synthesis Example 1
(1) was partly dried at a temperature of 105.degree. C. under
reduced pressure for 2 hours so that the solvent was thoroughly
removed to isolate the vinyl polymer. The vinyl polymer thus
isolated was then measured for molecular weight by gel permeation
chromatography with polystyrene as a standard material and
tetrahydrofuran as a solvent. As a result, the vinyl polymer was
found to have a weight-average molecular weight of about
10,000.
The vinyl polymer was also measured for Tg by means of a
differential scanning calorimeter. As a result, the vinyl polymer
was found to have Tg of 130.degree. C.
The vinyl polymer was further measured for AV by the method
according to JIS K 0070. As a result, the vinyl polymer was found
to have AV of 53.
(3) Preparation of Aqueous Dispersion of "Vinyl Polymer 1"
To the solution of "Vinyl Polymer 1" obtained in Synthesis Example
1 (1) was then added 1,000 parts of acetone. To the solution were
then added 98 parts of a 30% aqueous solution of ammonia with
stirring so that the salt-producing group in the vinyl polymer was
partly neutralized. To the solution were then added 1,500 parts of
ion-exchanged water. Methyl ethyl ketone and acetone were then
completely removed at a temperature of 60.degree. C. under reduced
pressure. Water was partly removed to concentrate the solution.
Thus, a water dispersion of "Vinyl Polymer 1" of Synthesis Example
1 having a solid concentration of 50% by weight was obtained.
Synthesis Example 2
(1) Synthesis of "Vinyl Polymer 2"
Into a reaction vessel equipped with an agitator, a reflux
condenser, a dropping funnel, a thermometer and a nitrogen inlet
pipe were charged 20 parts of methyl ethyl ketone as a
polymerization solvent and 6 parts of benzyl methacrylate, 2 parts
of polyethylene glycol methacrylate, 5 parts of methacrylic acid, 7
parts of tert-octylacrylamide and 0.6 part of tert-dodecyl
mercaptan as polymerizable unsaturated monomers. The air within the
reaction vessel was then thoroughly replaced by nitrogen gas.
Separately, into the dropping funnel in which the air within had
been thoroughly replaced by nitrogen gas were charged 24 parts of
benzyl methacrylate, 8 parts of polyethylene glycol methacrylate,
20 parts of methacrylic acid, 28 parts of tert-octylacrylamide, 2.4
parts of tert-dodecyl mercaptan, 60 parts of methyl ethyl ketone,
and 0.2 part of 2,2'-azobis(2,4-dimethylvaleronitrile).
In a nitrogen atmosphere, the mixture in the reaction vessel was
then heated to a temperature of 65.degree. C. with stirring. At
this temperature, the mixture in the dropping funnel was then
gradually added dropwise to the mixture in the reaction vessel in 3
hours. When 2 hours passed after the termination of dropwise
addition, to the mixture was then added a solution of 0.1 part of
2,2'-azobis(2,4-dimethylvaleronitrile) in 5 parts of methyl ethyl
ketone. The mixture was then subjected to ripening at a temperature
of 65.degree. C. for 2 hours and at a temperature of 70.degree. C.
for 2 hours to obtain "Vinyl Polymer 2".
(2) Measurement of Weight-Average Molecular Weight, Glass
Transition temperature (Tg) and Acid Value (AV) of "Vinyl Polymer
2"
The solution of "Vinyl Polymer 2" obtained in Synthesis Example 2
(1) was partly dried at a temperature of 105.degree. C. under
reduced pressure for 2 hours so that the solvent was thoroughly
removed to isolate the vinyl polymer. The vinyl polymer thus
isolated was then measured for molecular weight by gel permeation
chromatography with polystyrene as a standard material and
tetrahydrofuran as a solvent. As a result, the vinyl polymer was
found to have a weight-average molecular weight of about
10,000.
The vinyl polymer was also measured for Tg by means of a
differential scanning calorimeter. As a result, the vinyl polymer
was found to have Tg of 100.degree. C.
The vinyl polymer was further measured for AV by the method
according to JIS K 0070. As a result, the vinyl polymer was found
to have AV of 32.
(3) Preparation of Aqueous Dispersion of "Vinyl Polymer 2"
To the solution of "Vinyl Polymer 2" obtained in Synthesis Example
2 (1) was then added 1,000 parts of acetone. To the solution were
then added 98 parts of a 30% aqueous solution of ammonia with
stirring so that the salt-producing group in the vinyl polymer was
partly neutralized. To the solution were then added 1,500 parts of
ion-exchanged water. Methyl ethyl ketone and acetone were then
completely removed at a temperature of 60.degree. C. under reduced
pressure. Water was partly removed to concentrate the solution.
Thus, a water dispersion of "Vinyl Polymer 2" of Synthesis Example
2 having a solid concentration of 50% by weight was obtained.
Example 1
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
15 parts of carbon black ("MA-7" produced by MITSUBISHI CHEMICAL
CORPORATION) were mixed with 200 parts of sulfolane. The mixture
was then subjected to dispersion with a percent bead packing of 70%
at a rotary speed of 5,000 rpm by means of a Type M250 Eiger motor
mill (produced by Eiger Japan K.K.) for 1 hour. The mixture of
dispersed pigment paste and solvent was transferred into an
evaporator where it was then heated to a temperature of 120.degree.
C. under a pressure of not higher than 30 mmHg to distill off water
content contained in the system as much as possible. The
temperature of the solution was then controlled to 150.degree.
C.
Subsequently, to the solution were added 25 parts of sulfur
trioxide. The mixture was then allowed to undergo reaction for 6
hours. After the termination of the reaction, the reaction solution
was washed with excessive sulfolane several times, poured into
water, and then filtered to obtain a slurry of a surface-treated
carbon black pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated carbon black pigment obtained in
Example 1 (1) were added 2 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 10 parts of
Joncryl 679 (trade name of alkali-soluble resin produced by Johnson
Polymer Corporation, styrene-acrylic acid copolymer, Tg: 85.degree.
C., Mw: 7,000, AV: 200) as a resin, 7.5 parts of triethanolamine as
a neutralizing agent, and 60.5 parts of ion-exchanged water. The
mixture was then subjected to dispersion by means of a paint shaker
(using glass beads; percent bead packing: 60%; medium diameter: 1.7
mm) until the average particle diameter (secondary particle
diameter) of the pigment reached 100 nm to obtain a dispersion of a
surface-treated carbon black pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof (surface tension: 33 mN/m). The
dispersion time was about 1 hour.
In Example 1, a resin was added at the dispersion step to prepare a
pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 40 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 2 (1) were gradually added 0.2 part of
Surfynol 465, 10 parts of triethylene glycol mono-n-butyl ether, 15
parts of glycerin, 2.5 parts of 1,5-pentanediol, and 32.3 parts of
ion-exchanged water with stirring to obtain the ink of Example 1
(black ink). The formulation of the ink will be shown in detail
below.
Surface-treated carbon black pigment 8.0% (as of Example 1 (1)
calculated in terms of solid content) Joncryl 679 8.0% Surfynol 465
1.0% Triethylene glycol monobutyl ether 10.0% Glycerin 15.0%
1,5-Pentanediol 2.5% Triethanolamine 3.0% Ion-exchanged water
Balance
(The amount of the surface-treated carbon black pigment, Surfynol
465, Joncryl 679, triethanolamine, and ion-exchanged water in the
ink composition include that added as components of the dispersion
of surface-treated carbon black pigment)
Example 2
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
In Example 2, as a surface-treated pigment there was used the
surface-treated carbon black pigment prepared in Example 1 (1) as
such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated carbon black pigment obtained in
Example 1 (1) were added 2.5 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 20 parts of an
acrylic acid-methacrylic acid ester copolymer which is an
alkali-soluble resin (Tg: 75.degree. C.; Mw: 2,500; AV: 200) as a
resin, 12.5 parts of triethanolamine as a neutralizing agent, and
45 parts of ion-exchanged water. The mixture was then subjected to
dispersion by means of a paint shaker (using glass beads; percent
bead packing: 60%; medium diameter: 1.7 mm) until the average
particle diameter (secondary particle diameter) of the pigment
reached 100 nm to obtain a dispersion of a surface-treated carbon
black pigment having a sulfur-containing dispersibility-providing
group such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic
acid group (SO.sub.3.sup.-) directly introduced onto the surface
thereof (surface tension: 35 mN/m). The dispersion time was about 1
hour.
In Example 2, a resin was added at the dispersion step to prepare a
pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 40 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 2 (2) were gradually added 10 parts of
triethylene glycol mono-n-butyl ether, 15 parts of glycerin, 2.5
parts of 1,5-pentanediol, and 32.5 parts of ion-exchanged water
with stirring to obtain the ink of Example 2 (black ink). The
formulation of the ink will be shown in detail below.
Surface-treated carbon black pigment 8.0% (as of Example 1 (1)
calculated in terms of solid content) Acrylic acid-methacrylic acid
8.0% ester copolymer Surfynol 465 1.0% Triethylene glycol
mono-n-butyl ether 10.0% Glycerin 15.0% 1,5-Pentanediol 2.5%
Triethanolamine 5.0% Ion-exchanged water Balance
(The amount of the surface-treated carbon black pigment, Surfynol
465, acrylic acid-methacrylic acid ester copolymer,
triethanolamine, and ion-exchanged water in the ink composition
include that added as components of the dispersion of
surface-treated carbon black pigment)
Example 3
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
In Example 3, as a surface-treated pigment there was used the
surface-treated carbon black pigment prepared in Example 1 (1) as
such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated carbon black pigment obtained in
Example 1 (1) were added 2 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 2 parts of
triethanolamine as a neutralizing agent, and 26 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 100
nm. The dispersion time was about 1 hour.
(Addition of Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion was then gradually added a resin
solution prepared from 20 parts of Joncryl 682 (trade name of
styrene-acrylic acid copolymer which is an alkali-soluble resin
produced by Johnson Polymer Co., Ltd.; Tg: 57.degree. C.; Mw:
1,600; AV: 235) as a resin, 12.5 parts of triethanolamine as a
neutralizing agent, and 17.5 parts of ion-exchanged water with
stirring to obtain a dispersion of a surface-treated carbon black
pigment having a sulfur-containing dispersibility-providing group
such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid
group (SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 30 mN/m)
In Example 3, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 40 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 3 (2) were gradually added 0.2 part of
Surfynol 465, 10 parts of triethylene glycol mono-n-butyl ether, 15
parts of glycerin, 2.5 parts of 1,5-pentanediol, and 32.3 parts of
ion-exchanged water with stirring to obtain the ink of Example 3
(black ink). The formulation of the ink will be shown in detail
below.
Surface-treated carbon black pigment 8.0% (as of Example 1 (1)
calculated in terms of solid content) Joncryl 682 8.0% Surfynol 465
1.0% Triethylene glycol mono-n-butyl ether 10.0% Glycerin 15.0%
1,5-Pentanediol 2.5% Triethanolaniine 5.8% Ion-exchanged water
Balance
(The amount of the surface-treated carbon black pigment, Surfynol
465, Joncryl 682, triethanolamine, and ion-exchanged water in the
ink composition include that added as components of the dispersion
of surface-treated carbon black pigment)
Example 4
(1) Preparation of Surface-treated Pigment: C.I. Pigment Blue
15:3
(Surface Treatment Step)
20 parts of a phthalocyanine blue pigment (C.I. pigment blue 15:3)
were mixed with 500 parts of quinoline. The mixture was then
subjected to dispersion with a percent bead packing of 70% at a
rotary speed of 5,000 rpm by means of a Type M250 Eiger motor mill
(produced by Eiger Japan K.K.) for 2 hours. The mixture of
dispersed pigment paste and solvent was transferred into an
evaporator where it was then heated to a temperature of 120.degree.
C. under a pressure of not higher than 30 mmHg to distill off water
content contained in the system as much as possible. The
temperature of the solution was then controlled to 160.degree. C.
Subsequently, to the solution were added 20 parts of sulfonated
pyridine complex. The mixture was then allowed to undergo reaction
for 8 hours. After the termination of the reaction, the reaction
solution was washed with excessive quinoline several times, poured
into water, and then filtered to obtain a slurry of a
surface-treated phthalocyanine blue pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated phthalocyanine blue pigment
obtained in Example 4 (1) were added 2 parts of Surfynol 465 (trade
name, produced by Air Products Inc.) as a wetting agent, 6 parts of
monoethanolamine as a neutralizing agent, and 67 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 95
nm. The dispersion time was about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion were then added 5 parts of Joncryl 68
(trade name of styrene-acrylic acid copolymer which is an
alkali-soluble resin produced by Johnson Polymer Co., Ltd.; Tg:
70.degree. C.; Mw: 10,000; AV:195) with stirring. The mixture was
then stirred to make a solution. Thus, a dispersion of a
surface-treated phthalocyanine blue pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 33 mN/m) was obtained.
In Example 4, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 4, to 30 parts of the dispersion of surface-treated
phthalocyanine blue pigment obtained in Example 4 (2) were
gradually added 0.2 part of Surfynol 465, 7.5 parts of diethylene
glycol mono-n-butyl ether, 10 parts of glycerin, 5 parts of
1,2-hexanediol, 0.2 part of trishydroxymethylaminomethane, 0.03
part of hexachlorophene, and 47.07 parts of ion-exchanged water
with stirring to obtain the ink of Example 4 (cyan ink). The
formulation of the ink will be shown in detail below.
Surface-treated phthalocyanine blue pigment 6.0% (as of Example 4
(1) calculated in terms of solid content) Joncryl 68 1.5% Surfynol
465 0.8% Diethylene glycol mono-n-butyl ether 7.5% Glycerin 10.0%
1,2-Hexanediol 5.0% Monoethanolamine 2.0%
Trishydroxymethylaminomethane 0.2% Hexachlorophene 0.03%
Ion-exchanged water Balance
(The amount of the surface-treated phthalocyanine blue pigment,
Surfynol 465, Joncryl 68, monoethanolamine, and ion-exchanged water
in the ink composition include that added as components of the
dispersion of surface-treated phthalocyanine blue pigment)
Example 5
(1) Preparation of Surface-treated Pigment: C.I. Pigment Blue
15:3
(Surface Treatment Step)
In Example 5, as a surface-treated pigment there was used the
surface-treated phthalocyanine blue pigment prepared in Example 4
(1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated phthalocyanine blue pigment
obtained in Example 4 (1) were added 2 parts of Surfynol 465 (trade
name, produced by Air Products Inc.) and 5 parts of diethylene
glycol mono-n-butyl ether as wetting agents, 5 parts of Joncryl 550
(trade name of styrene-acrylic acid copolymer which is an
alkali-soluble resin, produced by Johnson Polymer Co., Ltd.; Tg:
75.degree. C.; Mw: 7,500; AV: 200) as a resin, 6 parts of
monoethanolamine as a neutralizing agent, and 62 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 95 nm
to obtain a dispersion of a surface-treated phthalocyanine blue
pigment having a sulfur-containing dispersibility-providing group
such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid
group (SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 30 mN/m). The dispersion time was about 1
hour.
In Example 5, a resin was added at the dispersion step to prepare a
pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 5, to 30 parts of the dispersion of surface-treated
phthalocyanine blue pigment obtained in Example 5 (2) were
gradually added 0.2 part of Surfynol 465, 6 parts of diethylene
glycol mono-n-butyl ether, 10 parts of glycerin, 5 parts of
1,2-hexanediol, 0.2 part of trishydroxymethylaminomethane, 0.03
part of hexachlorophene, and 48.57 parts of ion-exchanged water
with stirring to obtain the ink of Example 5 (cyan ink). The
formulation of the ink will be shown in detail below.
Surface-treated phthalocyanine blue pigment 6.0% (as of Example 4
(1) calculated in terms of solid content) Joncryl 550 1.5% Surfynol
465 0.8% Diethylene glycol mono-n-butyl ether 7.5% Glycerin 10.0%
1,2-Hexanediol 5.0% Monoethanolamine 2.0%
Trishydroxymethylaminomethane 0.2% Hexachlorophene 0.03%
Ion-exchanged water Balance
(The amount of the surface-treated phthalocyanine blue pigment,
Surfynol 465, Joncryl 550, monoethanolamine, and ion-exchanged
water in the ink composition include that added as components of
the dispersion of surface-treated phthalocyanine blue pigment)
Example 6
(1) Preparation of Surface-treated Pigment: C.I. Pigment Blue
15:3
Surface Treatment Step
In Example 6, as a surface-treated pigment there was used the
surface-treated phthalocyanine blue pigment prepared in Example 4
(1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated phthalocyanine blue pigment
obtained in Example 4 (1) were added 1 part of Surfynol 485 (trade
name, produced by Air Products Inc.) and 0.5 part of Surfynol 104
as wetting agents, 20 parts of a 50% aqueous emulsion of Vinyl
Polymer 1 prepared in Synthesis Example 1 (Tg: 130.degree. C.; Mw:
10,000; AV: 53) as a resin, 5 parts of diethanolamine as a
neutralizing agent, and 53.5 parts of ion-exchanged water. The
mixture was then subjected to dispersion by means of a paint shaker
(using glass beads; percent bead packing: 60%; medium diameter: 1.7
mm) until the average particle diameter (secondary particle
diameter) of the pigment reached 95 nm to obtain a dispersion of a
surface-treated phthalocyanine blue pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface there of
(surface tension: 34 mN/m). The dispersion time was about 1
hour.
In Example 6, a resin was added at the dispersion step to prepare a
pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 6, to 30 parts of the dispersion of surface-treated
phthalocyanine blue pigment obtained in Example 6 (2) were
gradually added 2 parts of triethylene glycol mono-n-butyl ether,
10 parts of glycerin, 5 parts of triethylene glycol, 6 parts of
1,2-hexanediol, and 47 parts of ion-exchanged water with stirring
to obtain the ink of Example 6 (cyan ink). The formulation of the
ink will be shown in detail below.
Surface-treated phthalocyanine blue pigment 6.0% (as of Example 4
(1) calculated in terms of solid content) Vinyl Polymer 1 3.0% (as
calculated in terms of solid content) Surfynol 485 0.3% Surfynol
104 0.15% Triethylene glycol mono-n-butyl ether 2.0% Glycerin 10.0%
Triethylene glycol 5.0% 1,2-Hexanediol 6.0% Diethanolamine 1.5%
Ion-exchanged water Balance
(The amount of the surface-treated phthalocyanine blue pigment,
Vinyl Polymer 1, Surfynol 485, Surfynol 104, diethanolamine, and
ion-exchanged water in the ink composition include that added as
components of the dispersion of surface-treated phthalocyanine blue
pigment)
Example 7
(1) Preparation of Surface-treated Pigment: C.I. Pigment Yellow
110
(Surface Treatment Step)
20 parts of an isoindolinone pigment (C.I. pigment yellow 110) were
mixed with 500 parts of quinoline. The mixture was then subjected
to dispersion with a percent bead packing of 70% at a rotary speed
of 5,000 rpm by means of a Type M250 Eiger motor mill (produced by
Eiger Japan K.K.) for 2 hours. The mixture of dispersed pigment
paste and solvent was transferred into an evaporator where it was
then heated to a temperature of 120.degree. C. under a pressure of
not higher than 30 mmHg to distill off water content contained in
the system as much as possible. The temperature of the solution was
then controlled to 160.degree. C. Subsequently, to the solution
were added 20 parts of sulfonated pyridine complex as a reacting
agent. The mixture was then allowed to undergo reaction for 4
hours. After the termination of the reaction, the reaction solution
was washed with excessive quinoline several times, poured into
water, and then filtered to obtain a surface-treated particulate
isoindolinone pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated isoindolinone pigment obtained
in Example 7 (1) were added 10 parts of diethylene glycol
mono-n-butyl ether as a wetting agent, 40 parts of Joncryl 682
(trade name of styrene-acrylic acid copolymer which is an
alkali-soluble resin produced by Johnson Polymer Co., Ltd.; Tg:
57.degree. C.; Mw: 1,600; AV: 235) as a resin, 10 parts of a 30%
aqueous solution of ammonia as a neutralizing agent, and 20 parts
of ion-exchanged water. The mixture was then subjected to
dispersion by means of a paint shaker (using glass beads; percent
bead packing: 60%; medium diameter: 1.7 mm) until the average
particle diameter (secondary particle diameter) of the pigment
reached 90 nm (surface tension: 39 mN/m). The dispersion time was
about 1 hour.
In Example 7, a resin was added at the dispersion step to prepare a
pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 7, to 22.5 parts of the dispersion of surface-treated
isoindolinone pigment obtained in Example 7 (2) were gradually
added 7.75 parts of diethylene glycol mono-n-butyl ether, 12 parts
of glycerin, 0.2 part of polyoxyethylene (EO=8) nonylphenyl ether,
5 parts of 1,5-pentanediol, 3 parts of 1-propanol, 3 parts of urea,
and 46.55 parts of ion-exchanged water with stirring to obtain the
ink of Example 7 (yellow ink). The formulation of the ink will be
shown in detail below.
Surface-treated isoindolinone pigment 4.5% (as of Example 7 (1)
calculated in terms of solid content) Joncryl 682 9.0% Diethylene
glycol monobutyl ether 10.0% Glycerin 12.0% Polyoxyethylene (EO =
8) nonylphenyl 0.2% ether 1,5-Pentanediol 5.0% 1-Propanol 3.0% 30%
Aqueous solution of ammonia 2.25% Urea 3.0% Ion-exchanged water
Balance
(The amount of the surface-treated isoindolinone pigment, Joncryl
682, diethylene glycol mono-n-butyl ether, ammonia, and
ion-exchanged water in the ink composition include that added as
components of the dispersion of surface-treated isoindolinone
pigment)
Example 8
(1) Preparation of Surface-treated Pigment: C.I. Pigment Yellow
110
(Surface Treatment Step)
In Example 8, there was used the surface-treated isoindolinone
pigment having a sulfur-containing dispersibility-providing group
such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid
group (SO.sub.3.sup.-) directly introduced onto the surface thereof
prepared in Example 7 (1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated isoindolinone pigment obtained
in Example 7 (1) were added 10 parts of diethylene glycol
mono-n-butyl ether as a wetting agent, 10 parts of a 30% aqueous
solution of ammonia as a neutralizing agent, and 20 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 90
nm. The dispersion time was about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion was then gradually added a resin
solution prepared from 40 parts of Joncryl 586 (trade name of
styrene-acrylic acid copolymer which is an alkali-soluble resin
produced by Johnson Polymer Co., Ltd.; Tg: 63.degree. C.; Mw:
3,100; AV: 105) as a resin with stirring to obtain a dispersion of
a surface-treated isoindolinone pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof (surface tension: 38 mN/m).
In Example 8, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 22.5 parts of the dispersion of surface-treated isoindolinone
pigment obtained in Example 8 (2) were gradually added 7.75 parts
of diethylene glycol mono-n-butyl ether, 12 parts of glycerin, 0.2
part of polyoxyethylene (EO=8) nonylphenyl ether, 5 parts of
1,5-pentanediol, 3 parts of 1-propanol, 3 parts of urea and 46.55
parts of ion-exchanged water with stirring to obtain the ink of
Example 8 (yellow ink). The formulation of the ink will be shown in
detail below.
Surface-treated isoindolinone pigment 4.5% (as of Example 7 (1)
calculated in terms of solid content) Joncryl 586 9.0% Diethylene
glycol monobutyl ether 10.0% Glycerin 12.0% Polyoxyethylene (EO =
8) nonylphenyl 0.2% ether 1,5-Pentanediol 5.0% 1-Propanol 3.0% 30%
Aqueous solution of ammonia 2.25% Urea 3.0% Ion-exchanged water
Balance
(The amount of the surface-treated isoindolinone pigment, Joncryl
586, diethylene glycol mono-n-butyl ether, ammonia, and
ion-exchanged water in the ink composition include that added as
components of the dispersion of surface-treated carbon black
pigment)
Example 9
(1) Preparation of Surface-treated Pigment: C.I. Pigment Yellow
110
(Surface Treatment Step)
In Example 9, there was used the surface-treated isoindolinone
pigment having a sulfur-containing dispersibility-providing group
such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid
group (SO.sub.3.sup.-) directly introduced onto the surface thereof
prepared in Example 7 (1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 15 parts of the surface-treated isoindolinone pigment obtained
in Example 7 (1) were added 3 parts of Acetylenol E-H (trade name,
produced by Kawaken Fine Chemicals, Co., Ltd.) and 20 parts of
triethylene glycol mono-n-butyl ether as a wetting agent, 2 parts
of tri-iso-propanol amine as a neutralizing agent, and 30 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 95
nm. The dispersion time was about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion were then added 30 parts of a 50%
aqueous emulsion of Vinyl Polymer 2 prepared in Synthesis Example 2
(Tg: 100.degree. C.; Mw: 10,000; AV: 32) as a resin with stirring.
The mixture was then stirred to obtain a dispersion of a
surface-treated isoindolinone pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof (surface tension: 30 mN/m).
In Example 9, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 9, to 20 parts of the dispersion of surface-treated
isoindolinone pigment obtained in Example 9 (2) were gradually
added 6 parts of an aqueous emulsion of Vinyl Polymer 2,4 parts of
diethylene glycol mono-n-butyl ether, 15 parts of glycerin, 0.6
part of Acetylenol E-H, and 54.4 parts of ion-exchanged water with
stirring to obtain the ink of Example 9 (yellow ink). The
formulation of the ink will be shown in detail below.
Surface-treated isoindolinone pigment 3.0% (as of Example 7 (1)
calculated in terms of solid content) Vinyl Polymer 2 6.0% (as
calculated in terms of solid content) Diethylene glycol monobutyl
ether 4.0% Triethylene glycol mono-n-butyl 4.0% ether Glycerin
15.0% Tri-iso-propanolamine 0.4% Ion-exchanged water Balance
(The amount of the surface-treated isoindolinone pigment, Vinyl
Polymer 2, triethylene glycol mono-n-butyl ether,
tri-iso-propanolamine, and ion-exchanged water in the ink
composition include that added as components of the dispersion of
surface-treated isoindolinone pigment)
Example 10
(1) Preparation of Surface-treated Pigment: C.I. Pigment Red
122
(Surface Treatment Step)
20 parts of a dimethyl quinacridone pigment (C.I. pigment red 122)
were mixed with 500 parts of quinoline. The mixture was then
subjected to dispersion with a percent bead packing of 70% at a
rotary speed of 5,000 rpm by means of a Type M250 Eiger motor mill
(produced by Eiger Japan K.K.) for 2 hours. The mixture of
dispersed pigment paste and solvent was transferred into an
evaporator where it was then heated to a temperature of 120.degree.
C. under a pressure of not higher than 30 mmHg to distill off water
content contained in the system as much as possible. The
temperature of the solution was then controlled to 160.degree. C.
Subsequently, to the solution were added 20 parts of sulfonated
pyridine complex as a reacting agent. The mixture was then allowed
to undergo reaction for 4 hours. After the termination of the
reaction, the reaction solution was washed with excessive quinoline
several times, poured into water, and then filtered to obtain a
slurry of a surface-treated dimethyl quinacridone pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated dimethyl quinacridone pigment
obtained in Example 10 (1) were added 5 parts of Surfynol 465
(trade name, produced by Air Products Inc.) and 10 parts of
1,5-pentanedil as wetting agents, 1 part of a 30% aqueous solution
of ammonia as a neutralizing agent, and 62 parts of ion-exchanged
water. The mixture was then subjected to dispersion by means of a
paint shaker (using glass beads; percent bead packing: 60%; medium
diameter: 1.7 mm) until the average particle diameter (secondary
particle diameter) of the pigment reached 100 nm. The dispersion
time was about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion were then added 2 parts of a
styrene-acrylic acid copolymer which is an alkali-soluble resin
(Tg: 50.degree. C.; Mw: 25,000; AV: 250) as a resin with stirring.
The mixture was then stirred to make a resin solution. Thus, a
dispersion of a surface-treated dimethyl quinacridone pigment
having a sulfur-containing dispersibility-providing group such as
sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 35 mN/m) was obtained.
In Example 10, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 10, to 35 parts of the dispersion of surface-treated
dimethyl quinacridone pigment obtained in Example 10 (2) were
gradually added 0.25 part of Surfynol 465, 1.5 parts of
1,5-pentanediol, 12 parts of glycerin, 0.2 part of polyoxyethylene
(EO=8) nonylphenyl ether, 3 parts of 1-propanol, 0.05 part of a 30%
aqueous solution of ammonia, 3 parts of urea, and 45 parts of
ion-exchanged water with stirring to obtain the ink of Example 10
(magenta ink). The formulation of the ink will be shown in detail
below.
Surface-treated dimethyl quinacridone 7.0% (as pigment of Example
10 (1) calculated in terms of solid content) Styrene-acrylic acid
copolymer 0.7% Surfynol 465 2.0% Glycerin 12.0% Polyoxyethylene (EO
= 8) nonylphenyl 0.2% ether 1,5-Pentanediol 5.0% 1-Propanol 3.0%
30% Aqueous solution of ammonia 0.4% Urea 3.0% Ion-exchanged water
Balance
(The amount of the surface-treated dimethyl quinacridone pigment,
styrene-acrylic acid copolymer, Surfynol 465, 1,5-pentanediol,
ammonia, and ion-exchanged water in the ink composition include
that added as components of the dispersion of surface-treated
dimethyl quinacridone pigment)
Example 11
(1) Preparation of Surface-treated Pigment: C.I. Pigment Red
122
(Surface Treatment Step)
In Example 11, there was used the surface-treated dimethyl
quinacridone pigment prepared in Example 10 (1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated dimethyl quinacridone pigment
obtained in Example 10 (1) were added 5 parts of Surfynol 465
(trade name, produced by Air Products Inc.) and 10 parts of
1,5-pentanediol as wetting agents, 2 parts of Joncryl 683 (trade
name of styrene-acrylic acid copolymer which is an alkali-soluble
resin produced by Johnson Polymer Co., Ltd.; Tg: 63.degree. C.; Mw:
7,300; AV: 150) as a resin, 1 part of a 30% aqueous solution of
ammonia as a neutralizing agent, and 62 parts of ion-exchanged
water. The mixture was then subjected to dispersion by means of a
paint shaker (using glass beads; percent bead packing: 60%; medium
diameter: 1.7 mm) until the average particle diameter (secondary
particle diameter) of the pigment reached 100 nm to obtain a
dispersion of a surface-treated dimethyl quinacridone pigment
having a sulfur-containing dispersibility-providing group such as
sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface there of
(surface tension: 30 mN/m) The dispersion time was about 1
hour.
In Example 11, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 11, to 35 parts of the dispersion of surface-treated
dimethyl quinacridone pigment obtained in Example 11 (2) were
gradually added 0.25 part of Surfynol 465, 1.5 parts of
1,5-pentanediol, 12 parts of glycerin, 0.2 part of polyoxyethylene
(EO=8) nonylphenyl ether, 3 parts of 1-propanol, 0.05 part of a 30%
aqueous solution of ammonia, 3 parts of urea, and 45 parts of
ion-exchanged water with stirring to obtain the ink of Example 11
(magenta ink). The formulation of the ink will be shown in detail
below.
Surface-treated dimethyl quinacridone pigment of Example 10 (1)
7.0% (as calculated in terms of solid content) Joncryl 683 0.7%
Surfynol 465 2.0% Glycerin 12.0% Polyoxyethylene (EO = 8)
nonylphenyl 0.2% ether 1,5-Pentanediol 5.0% 1-Propanol 3.0% 28%
Aqueous solution of ammonia 0.4% Urea 3.0% Ion-exchanged water
Balance
(The amount of the surface-treated dimethyl quinacridone pigment,
Joncryl 683, Surfynol 465, 1,5-pentanediol, ammonia, and
ion-exchanged water in the ink composition include that added as
components of the dispersion of surface-treated dimethyl
quinacridone pigment)
Example 12
(1) Preparation of Surface-treated Pigment: C.I. Pigment Violet
19
(Surface Treatment Step)
20 parts of a quinacridone pigment (C.I. pigment violet 19) which
had been previously finely ground were mixed with 500 parts of
quinoline. The mixture was then thoroughly stirred by a magnetic
stirrer. The mixture of dispersed pigment paste and solvent thus
obtained was transferred into an evaporator where it was then
heated to a temperature of 120.degree. C. under a pressure of not
higher than 30 mmHg to distill off water content contained in the
system as much as possible. The temperature of the solution was
then controlled to 160.degree. C. Subsequently, to the solution
were added 20 parts of sulfonated pyridine complex. The mixture was
then allowed to undergo reaction for 8 hours. After the termination
of the reaction, the reaction solution was washed with excessive
quinoline several times, poured into water, and then filtered to
obtain a slurry of a surface-treated quinacridone pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 10 parts of the surface-treated quinacridone pigment obtained in
Example 12 (1) were added 3 parts of Surfynol 420 (produced by Air
Products Inc.) and 5 parts of 1,2-hexanediol as wetting agents, 60
parts of a 50% aqueous solution of Vinyl Polymer2prepared in
Synthesis Example 2 (Tg: 100.degree. C.; Mw: 10,000; AV: 32) as a
resin, 3 parts of tri-iso-propanolamine as a neutralizing agent, 5
parts of 2-pyrrolidone as a dissolution aid for Surfynol 420, and
14 parts of ion-exchanged water. The mixture was then subjected to
dispersion by means of a paint shaker (using glass beads; percent
bead packing: 60%; medium diameter: 1.7 mm) until the average
particle diameter (secondary particle diameter) of the pigment
reached 95 nm to obtain a surface-treated quinacridone pigment
dispersion having a sulfur-containing dispersibility-providing
group introduced therein (surface tension: 31 mN/m). The dispersion
time was about 1 hour.
In Example 12, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 20 parts of the dispersion of surface-treated quinacridone
pigment obtained in Example 12 (2) were gradually added 0.4 part of
Surfynol 420 (produced by Air Products Co., Ltd.), 1. 4 parts of
1,2-hexanediol, 3 parts of triethyleneglycol mono-n-butyl ether, 10
parts of glycerin, 5 parts of triethylene glycol, and 60.2 parts of
ion-exchanged water with stirring to obtain the ink of Example 12
(magenta ink). The formulation of the ink will be shown in detail
below.
Surface-treated quinacridone pigment of Example 12 (1) 2.0% (as
calculated in terms of solid content) Vinyl Polymer 2 6.0% (as
calculated in terms of solid content) Surfynol 420 1.0%
1,2-Hexanediol 2.4% 2-Pyrrolidone 1.0% Triethylene glycol
mono-n-butyl 3.0% ether Glycerin 10.0% Triethylene glycol 5.0%
Tri-iso-propanolamine 0.6% Ion-exchanged water Balance
(The amount of the surface-treated quinacridone pigment, Vinyl
Polymer 2, Surfynol 420, 1,2-hexanediol, 2-pyrrolidone,
tri-iso-propanolamine, and ion-exchanged water in the ink
composition include that added as components of the dispersion of
surface-treated quinacridone pigment)
Example 13
(1) Preparation of Surface-treated Pigment: C.I. Pigment Yellow
128
(Surface Treatment Step)
20 parts of a condensed azo yellow pigment (C.I. pigment red 128)
were mixed with 500 parts of quinoline. The mixture was then
subjected to dispersion for uniformalization of particle size with
a percent bead packing of 70% at a rotary speed of 5,000 rpm by
means of a Type M250 Eiger motor mill (produced by Eiger Japan
K.K.) for 2 hours. The mixture of dispersed pigment paste and
solvent thus obtained was transferred into an evaporator where it
was then heated to a temperature of 120.degree. C. under a pressure
of not higher than 30 mmHg to distill off water content contained
in the system as much as possible. The temperature of the solution
was then controlled to 160.degree. C. Subsequently, to the solution
were added 20 parts of sulfonated pyridine complex as a reacting
agent. The mixture was then allowed to undergo reaction for 4
hours. After the termination of the reaction, the reaction solution
was washed with excessive quinoline several times, poured into
water, and then filtered to obtain a slurry of a surface-treated
condensed azo yellow pigment having a sulfur-containing
dispersibility-providing group such as sulfinic acid group
(SO.sub.2.sup.-) and sulfonic acid group (SO.sub.3.sup.-) directly
introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 5 parts of the surface-treated condensed azo yellow pigment
obtained in Example 13 (1) were added 0.1 part of Acetylenol E-O
(produced by Kawaken Fine Chemicals Co., Ltd.) and 10 parts of
diethylene glcyol mono-n-butyl ether as wetting agents, 5 parts of
Joncryl B-36 (trade name of styrene-acrylic acid copolymer which is
an alkali-soluble resin produced by Johnson Polymer Co., Ltd.; Tg:
65.degree. C.; Mw: 6,800; AV: 250) and 5 parts of Joncryl 586
(trade name of styrene-acrylic acid copolymer which is an
alkali-soluble resin produced by Johnson Polymer Co., Ltd.; Tg:
63.degree. C.; Mw: 3,100; AV: 105) as resins, 2 parts of sodium
hydroxide as a neutralizing agent, and 72.9 parts of ion-exchanged
water. The mixture was then subjected to dispersion by means of a
paint shaker (using glass beads; percent bead packing: 60%; medium
diameter: 1.7 mm) until the average particle diameter (secondary
particle diameter) of the pigment reached 110 nm to obtain a
surface-treated condensed azo yellow pigment dispersion having a
sulfur-containing dispersibility-providing group introduced therein
(surface tension: 39 mN/m). The dispersion time was about 3
hours.
In Example 13, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Example 13, to 60 parts of the dispersion of surface-treated
condensed azo yellow pigment obtained in Example 13 (2) were
gradually added 0.5 part of Acetylenol E-H (produced by Kawaken
Fine Chemicals Co., Ltd.), 5 parts of glycerin, 10 parts of
tetraethylene glycol, and 24.5 parts of ion-exchanged water with
stirring to obtain the ink of Example 13 (yellow ink). The
formulation of the ink will be shown in detail below.
Surface-treated condensed azo yellow pigment of Example 13 (1) 3.0%
(as calculated in terms of solid content) Acetylenol E-O 0.06%
Acetylenol E-H 0.5% Joncryl B-36 3.0% Joncryl 586 3.0% Diethylene
glycol mono-n-butyl 6.0% ether Glycerin 5.0% Tetraethylene glycol
10.0% Sodium hydroxide 1.2% Ion-exchanged water Balance
(The amount of the surface-treated condensed azo yellow pigment,
Joncryl B-36, Joncryl 586, Acetylenol E-O, diethylene glycol
mono-n-butyl ether, sodium hydroxide, and ion-exchanged water in
the ink composition include that added as components of the
dispersion of surface-treated condensed azo yellow pigment)
Example 14
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
25 parts of a carbon black pigment ("Special Black 4", produced by
Degussa Inc.) were mixed with 250 parts of sulfolane. The mixture
was then subjected to dispersion for uniformalization of particle
size with a percent bead packing of 70% at a rotary speed of 5,000
rpm by means of a Type M250 Eiger motor mill (produced by Eiger
Japan K.K.) for 1 hour. The mixture of dispersed pigment paste and
solvent was transferred into an evaporator where it was then heated
to a temperature of 120.degree. C. under a pressure of not higher
than 30 mmHg to distill off water content contained in the system
as much as possible. The temperature of the solution was then
controlled to 150.degree. C. Subsequently, to the solution were
added 25 parts of sulfur trioxide. The mixture was then allowed to
undergo reaction for 6 hours. After the termination of the
reaction, the reaction solution was washed with excessive sulfolane
several times, poured into water, and then filtered to obtain a
slurry of a surface-treated carbon black pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof.
In Example 14, into the surface-treated carbon black pigment was
further introduced a polyethylene glycol (Mw: 5,000) as a polymer
material.
To 400 parts of water were then added 5 parts of ethyl
p-aminobenzoate and 3 parts of concentrated nitric acid. The
mixture was then cooled to a temperature of 5.degree. C. with
stirring. To the suspension thus obtained was then added the
foregoing surface-treated carbon black pigment. To the mixture was
then slowly added an aqueous solution of 50 parts of water and 2
parts of sodium nitrite with stirring in 10 hours. The mixture was
then repeatedly rinsed and filtered to obtain a slurry of a
surface-treated carbon black pigment further having a carboxylic
acid ethyl group introduced therein with the interposition of
phenyl group.
Subsequently, to a solution of 40 parts of a polyethylene glycol
(Mw: 5,000) and 0.5 part of diazabicycloundecene (DBU) in 200 parts
of ethanol was slowly added the surface-treated carbon black
pigment thus synthesized with stirring. The mixture was then
adjusted to a pH value of 10. The mixture was then refluxed for 24
hours. The mixture thus obtained was then repeatedly washed with
ethanol and filtered. Eventually, a surface-treated carbon black
pigment having a sulfur-containing dispersibility-providing group
directly introduced onto the surface thereof and a polyethylene
oxide propylene oxide benzamide introduced thereonto with the
interposition of phenyl group was obtained.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 30 parts of the surface-treated carbon black pigment obtained in
Example 14 (1) were added 2 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 6 parts of a 50%
aqueous emulsion of Vinyl Polymer 1 prepared in Synthesis Example 1
(Tg: 130.degree. C.; Mw: 10,000; AV: 53) as a resin, 2 parts of
diethanolamine as a neutralizing agent, and 60 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 100
nm to obtain a dispersion of a surface-treated carbon black pigment
having a sulfur-containing dispersibility-providing group directly
introduced onto the surface thereof (surface tension: 30 mN/m) The
dispersion time was about 1 hour.
In Example 14, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 20 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 14 (2) were gradually added 10 parts of
diethylene glycol mono-n-butyl ether, 15 parts of glycerin, and 55
parts of ion-exchanged water with stirring to obtain the ink of
Example 14 (black ink). The formulation of the ink will be shown in
detail below.
Surface-treated carbon black pigment of Example 14 (1) 6.0% (as
calculated in terms of solid content) Vinyl Polymer 1 0.6% (as
calculated in terms of solid content) Surfynol 465 0.4% Diethylene
glycol mono-n-butyl ether 10.0% Glycerin 15.0% Diethanolamine 0.4%
Ion-exchanged water Balance
(The amount of the surface-treated carbon black pigment, Vinyl
Polymer 1, Surfynol 465, driethanolamine, and ion-exchanged water
in the ink composition include that added as components of the
dispersion of surface-treated carbon black pigment)
Example 15
(1) Preparation of Surface-treated Pigment: C.I. Pigment Red
177
(Surface Treatment Step)
25 parts of a dianthraquinolyl red pigment which had been
previously ground (C.I. pigment red 177) were mixed with 480 parts
of quinoline. The mixture was then thoroughly stirred by means of a
magnetic stirrer. The mixture of pigment paste and solvent thus
obtained was transferred into an evaporator where it was then
heated to a temperature of 120.degree. C. under a pressure of not
higher than 30 mmHg to distill off water content contained in the
system as much as possible. The temperature of the solution was
then controlled to 160.degree. C. Subsequently, to the solution
were added 20 parts of sulfur trioxide. The mixture was then
allowed to undergo reaction for 8 hours. After the termination of
the reaction, the reaction solution was washed with excessive
quinoline several times, poured into water, and then filtered to
obtain a surface-treated dianthraquinolyl red pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof.
In Example 15, into the surface-treated dianthraquinolyl red
pigment was further introduced a polyethylene glycol (Mw: 2,000) as
a polymer material.
To 450 parts of water were then added 5 parts of ethyl
p-aminobenzoate and 3 parts of concentrated nitric acid. The
mixture was then cooled to a temperature of 5.degree. C. with
stirring. To the suspension thus obtained was then added the
foregoing surface-treated dianthraquinolyl red pigment. To the
mixture was then slowly added an aqueous solution of 50 parts of
water and 2 parts of sodium nitrite with stirring in 10 hours. The
mixture was then repeatedly rinsed and filtered to obtain a slurry
of a surface-treated dianthraquinolyl red pigment further having a
carboxylic acid ethyl group introduced therein with the
interposition of phenyl group.
Subsequently, to a solution of 35 parts of a polyethylene glycol
(Mw: 2,000) and 0.4 part of diazabicycloundecene (DBU) in 200 parts
of ethanol was slowly added the surface-treated dianthraquinolyl
red pigment thus synthesized with stirring. The mixture was then
adjusted to a pH value of 10. The mixture was then refluxed for 24
hours. The mixture thus obtained was then repeatedly washed with
ethanol and filtered. Eventually, a surface-treated
dianthraquinolyl red pigment having a sulfur-containing
dispersibility-providing group directly introduced onto the surface
thereof and a polyethylene oxide propylene oxide benzamide
introduced thereonto with the interposition of phenyl group was
obtained.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated dianthraquinolyl red pigment
obtained in Example 15 (1) were added 3 parts of Surfynol 420
(produced by Air Products Inc.) and5 parts of 1,2-hexanediol as
wetting agents, 4 parts of Joncryl 682 (trade name of
styrene-acrylic acid copolymer which is an alkali-soluble resin
produced by Johnson Polymer Co., Ltd.; Tg: 57.degree. C.; Mw:
1,600; AV: 235) as a resin, 5 parts of tri-iso-propanol as a
neutralizing agent, 5 parts of 2-pyrrolidone as a dissolution aid
for Surfynol 420, and 58 parts of ion-exchanged water. The mixture
was then subjected to dispersion by means of a paint shaker (using
glass beads; percent bead packing: 60%; medium diameter: 1.7 mm)
until the average particle diameter (secondary particle diameter)
of the pigment reached 95 nm to obtain a dispersion of a
surface-treated carbon black pigment having a sulfur-containing
dispersibility-providing group directly introduced onto the surface
thereof (surface tension: 31 mN/m) The dispersion time was about 1
hour.
In Example 15, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 30 parts of the dispersion of surface-treated dianthraquinolyl
red pigment obtained in Example 15 (2) were gradually added 1 part
of 1,2-hexanedil, 3 parts of triethylene glycol mono-n-butyl ether,
10 parts of glycerin, 5 parts of triethylene glycol, and 51 parts
of ion-exchanged water with stirring to obtain the ink of Example
15 (magenta ink). The formulation of the ink will be shown in
detail below.
Surface-treated dianthraquinolyl red pigment of Example 15 (1) 6.0%
(as calculated in terms of solid content) Joncryl 682 1.2% Surfynol
420 0.9% 1,2-Hexanediol 2.5% 2-Pyrrolidone 1.0% Triethylene glycol
mono-n-butyl 3.0% ether Glycerin 10.0% Triethylene glycol 5.0%
Tri-iso-propanolamine 1.5% Ion-exchanged water Balance
(The amount of the surface-treated dianthraquinolyl red pigment,
Joncryl 682, Surfynol 420, 1,2-hexanediol, 2-pyrrolidone,
tri-iso-propanolamine, and ion-exchanged water in the ink
composition include that added as components of the dispersion of
surface-treated dianthraquinolyl red pigment)
Example 16
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
35 parts of carbon black ("FW-18", produced by Degussa Inc.) were
mixed with 1,000 parts of water. The mixture was then subjected to
grinding by means of a ball mill. To the raw solution of ground
carbon black were then added 400 parts of sodium hypochlorite. The
mixture was further stirred for 10 hours at 90-110.degree. C. The
mixture was then repeatedly rinsed and filtered to obtain a slurry
of a surface-treated carbon black pigment having a
sulfur-containing dispersibility-providing group directly
introduced onto the surface thereof.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 15 parts of the surface-treated carbon black pigment obtained in
Example 16 (1) were added 1.5 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 5 parts of
Joncryl 68 (trade name of styrene-acrylic acid copolymer which is
an alkali-soluble resin produced by Johnson Polymer Co., Ltd.; Tg:
70.degree. C.; Mw: 10,000; AV: 195) as a resin, 1.5 parts of sodium
hydroxide as a neutralizing agent, and 77 parts of ion-exchanged
water. The mixture was then subjected to dispersion by means of a
paint shaker (using glass beads; percent bead packing: 60%; medium
diameter: 1.7 mm) until the average particle diameter (secondary
particle diameter) of the pigment reached 100 nm to obtain a
dispersion of a surface-treated carbon black pigment having a
carboxyl group introduced onto the surface thereof (surface
tension: 35 mN/m) The dispersion time was about 1 hour.
In Example 16, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 40 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 16 (2) were gradually added 10 parts of
diethylene glycol mono-n-butyl ether, 10 parts of glycerin, 5 parts
of thiodiglycol, 0.2 part of triethanolamine, and 34.8 parts of
ion-exchanged water with stirring to obtain the ink of Example 16
(black ink). The formulation of the ink will be shown in detail
below.
Surface-treated carbon black pigment of Example 16 (1) 6.0% (as
calculated in terms of solid content) Joncryl 68 2.0% Surfynol 465
0.6% Diethylene glycol mono-n-butyl 10.0% ether Glycerin 10.0%
Thiodiglycol 5.0% Sodium hydroxide 0.6% Trethanolamine 0.2%
Ion-exchanged water Balance
(The amount of the surface-treated carbon black pigment, Joncryl
68, Surfynol 465, sodium hydroxide, and ion-exchanged water in the
ink composition include that added as components of the dispersion
of surface-treated carbon black pigment)
Example 17
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
20 parts of carbon black ("FW-200", produced by Degussa Inc.) were
mixed with 200 parts of water. The mixture was then subjected to
grinding by means of a ball mill. To the raw solution of ground
carbon black were then added 7 parts of p-aminobenzenesulfonic acid
and 3 parts of nitric acid. The mixture was then stirred at a
temperature of 75.degree. C. for several hours. To the mixture was
then added a 20% aqueous solution of sodium nitrite. The mixture
was further stirred for 1 hour. The mixture was then repeatedly
rinsed and filtered to obtain a slurry of a surface-treated carbon
black pigment having a carboxyl group introduced therein with the
interposition of phenyl group.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated carbon black pigment obtained in
Example 17 (1) were added 2 parts of Florad 430 (produced by
Sumitomo 3M Co., Ltd.) and 5 parts of ethylene glycol monoethyl
ether as wetting agents, 5 parts of an acrylic acid-methacrylic
acid ester which is an alkali-soluble resin (Tg: 75.degree. C.; Mw:
2,500; AV: 200) and 5 parts of a 50% aqueous emulsion of Vinyl
Polymer 1 prepared in Synthesis Example 1 (Tg: 130.degree. C.; Mw:
10,000; AV: 53) as a resin, 4 parts of diethanolamine as a
neutralizing agent, and 59 parts of ion-exchanged water. The
mixture was then subjected to dispersion by means of a paint shaker
(using glass beads; percent bead packing: 60%; medium diameter: 1.7
mm) until the average particle diameter (secondary particle
diameter) of the pigment reached 110 nm to obtain a dispersion of a
surface-treated carbon black pigment (surface tension: 25 mN/m).
The dispersion time was about 1.5 hours.
In Example 17, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 30 parts of the dispersion of surface-treated carbon black
pigment obtained in Example 17 (2) were gradually added 3.5 parts
of ethylene glycol monoethyl ether, 0.5 part of Surfynol TG (trade
name, produced by Air Products Inc.), 8 parts of 2-pyrrolidone, 15
parts of glycerin, and 43 parts of ion-exchanged water with
stirring to obtain the ink of Example 17 (black ink). The
formulation of the ink will be shown in detail below.
Surface-treated carbon black pigment of Example 17 (1) 6.0% (as
calculated in terms of solid content) Acrylic acid-methacrylic acid
ester 1.5% Vinyl Polymer 1 0.75% (as calculated in terms of solid
content) Florad 430 0.6% Surfynol TG 0.5% 2-Pyrrolidone 8.0%
Ethylene glycol monoethyl ether 5.0% Glycerin 15.0% Diethanolamine
1.2% Ion-exchanged water Balance
(The amount of the surface-treated carbon black pigment, acrylic
acid-methacrylic acid ester, Vinyl Polymer 1, Florad 430, ethylene
glycol monoethyl ether, diethanolamine, and ion-exchanged water in
the ink composition include that added as components of the
dispersion of surface-treated carbon black pigment)
Example 18
(1) Preparation of Surface-treated Pigment: C.I. Pigment Green
7
(Surface Treatment Step)
20 parts of a phthalocyanine green pigment which had been
previously ground (C.I. pigment green 7) were mixed with 5 parts of
p-aminobenzenesulfonic acid. The mixture was then heated to a
temperature of 70.degree. C. To the mixture was then rapidly added
an aqueous solution of 2 parts of sodium nitrite in 80 parts of
water to form a pigment slurry. To the slurry thus obtained was
then added an aqueous solution of hydrogen chloride until the pH
value thereof reached 2. The slurry was stirred for 1 hour, and
then repeatedly rinsed and filtered to obtain a slurry of a
surface-treatedphthalocyanine green pigment having a sulfonic acid
group introduced therein with the interposition of phenyl
group.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 15 parts of the surface-treated phthalocyanine green pigment
obtained in Example 18 (1) were added 3 parts of FZ-2161 (trade
name, produced by Nippon Unicar Co., Ltd.) and 2 parts of
dipropylene glycol mono-n-butyl ether as wetting agents, 2 parts of
monoethanolamine as a neutralizing agent, and 18 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 110
nm. The dispersion time was about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion were then gradually added 60 parts of a
50% aqueous emulsion of Vinyl Polymer 2 prepared in Synthesis
Example 2 (Tg: 100.degree. C.; Mw: 10,000; AV: 32) as a resin with
stirring to obtain a dispersion of a surface-treated phthalocyanine
green pigment having a sulfonic acid group introduced therein with
the interposition of phenyl group (surface tension: 29 mN/M).
In Example 18, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 20 parts of the dispersion of surface-treated phthalocyanine
green pigment obtained in Example 18 (2) were gradually added 1.6
parts of dipropylene glycol mono-n-butyl ether, 5 parts of
2-pyrrolidone, 10 parts of glycerin, 5 parts of ethylene glycol,
and 58.4 parts of ion-exchanged water with stirring to obtain the
ink of Example 11. The formulation of the ink will be shown in
detail below.
Surface-treated phthalocyanine green pigment of Example 18 (1) 3.0%
(as calculated in terms of solid content) Vinyl Polymer 2 6.0% (as
calculated in terms of solid content) FZ-2161 0.6% Dipropylene
glycol mono-n-butyl 2.0% ether 2-Pyrrolidone 5.0% Glycerin 10.0%
Ethylene glycol 5.0% Monoethanolanline 0.4% Ion-exchanged water
Balance
(The amount of the surface-treated phthalocyanine green pigment,
Vinyl Polymer 2, FZ-2161, dipropylene glycol mono-n-butyl ether,
monoethanolamine, and ion-exchanged water in the ink composition
include that added as components of the dispersion of
surface-treated phthalocyanine green pigment)
Example 19
(1) Preparation of Surface-treated Pigment: C.I. Pigment Brown
32
(Surface Treatment Step)
In Example 19 (1), the procedure of Example 18 (1) was followed
except that as a pigment there was used a benzimidazolone brown
pigment (C.I. pigment brown 32). Thus, a surface-treated
benzimidazolone brown pigment having a sulfonic acid group
introduced therein with the interposition of phenyl group was
obtained.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 30 parts of the surface-treated benzimidazolone brown pigment
obtained in Example 19 (1) were added 10 parts of triethylene
glycol mono-n-butyl ether as a wetting agent, 3 parts of Joncryl
680 (trade name of styrene-acrylic acid copolymer which is an
alkali-soluble resin, produced by Johnson Polymer Co., Ltd.; Tg:
60.degree. C.; Mw: 3,900; AV: 215) as a resin, 5 parts of
triethanolamine as a neutralizing agent, and 52 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 120
nm to obtain a dispersion of a surface-treated benzimidazolone
brown pigment (surface tension: 39 mN/m). The dispersion time was
about 2 hours.
In Example 19, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 20 parts of the dispersion of surface-treated benzimidazolone
brown pigment obtained in Example 19 (2) were gradually added 1
part of Surfynol 465 (produced by Air Products Inc.), 15 parts of
glycerin, and 64 parts of ion-exchanged water with stirring to
obtain the ink of Example 19. The formulation of the ink will be
shown in detail below.
Surface-treated benzimidazolone brown pigment of Example 19 (1)
6.0% (as calculated in terms of solid content) Joncryl 680 0.6%
Surfynol 465 1.0% Triethylene glycol mono-n-butyl 2.0% ether
Glycerin 15.0% Trethanolamine 1.0% Ion-exchanged water Balance
(The amount of the surface-treated benzimidazolone brown pigment,
Joncryl 680, triethylene glycol mono-n-butyl ether,
triethanolamine, and ion-exchanged water in the ink composition
include that added as components of the dispersion of
surface-treated benzimidazolone brown pigment)
Example 20
(1) Preparation of Surface-treated Pigment: C.I. Pigment Red
149
(Surface Treatment Step)
50 parts of a perylene scarlet pigment which had been previously
finely ground (C.I. pigment red 149) were mixed with 6 parts of
p-aminobenzoic acid. To the mixture were then added 1.5 parts of
concentrated nitric acid and 200 parts of water. The mixture was
then cooled to a temperature of 5.degree. C. To the mixture was
then slowly added an aqueous solution of 1.2 parts of sodium
nitrite in 50 parts of water with stirring. Subsequently, the
mixture was heated to a temperature of 70.degree. C. with stirring
for 8 hours so that it underwent reaction, and then repeatedly
rinsed and filtered to obtain a pigment slurry.
To the foregoing pigment slurry were then added 6 parts of ethyl
p-aminobenzoate, 1.5 parts of concentrated nitric acid, 1.2 parts
of sodium nitrite, and 200 parts of water. The reaction mixture was
then allowed to undergo reaction in the same manner as mentioned
above. The reaction mixture was then repeatedly rinsed and filtered
to obtain a slurry of a surface-treated perylene scarlet pigment
having a carboxyl group and a carboxylic acid ethyl group
introduced therein with the interposition of phenyl group.
Subsequently, in Example 20, a polyethylene glycol (Mw: 2,000) was
further introduced into the surface-treated perylene scarlet
pigment as a polymer material.
In some detail, to a solution of 40 parts of apolyethylene glycol
(Mw: 2,000) and 0.3 parts of diazabicycloundecene (DBU) in 100
parts of ethanol was slowly added the surface-treated perylene
pigment synthesized above with stirring. Subsequently, the mixture
was adjusted to a pH value of 10, and then refluxed for 24
hours.
The mixture thus obtained was then repeatedly washed with ethanol
and filtered. Eventually, a surface-treated perylene scarlet
pigment having a carboxylic acid and polyethylene oxide propylene
oxide benzamide introduced therein with the interposition of phenyl
group was obtained.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated perylene scarlet pigment
obtained in Example 20 (1) were added 1 part of Surfynol 61
(produced by Air Products Inc.), 1 part of Surfynol 465 (produced
by Air Products Inc.) and 2 parts of propylene glycol mono-n-butyl
ether as wetting agents, 2 parts of Joncryl 682 (trade name of
styrene-acrylic acid copolymer which is an alkali-soluble resin
produced by Johnson Polymer Co., Ltd.; Tg: 57.degree. C.; Mw:
1,600; AV: 235) as a resin, 3 parts of triethanolamine as a
neutralizing agent, and 63.8 parts of ion-exchanged water. The
mixture was then subjected to dispersion by means of a paint shaker
(using glass beads; percent bead packing: 60%; medium diameter: 1.7
mm) until the average particle diameter (secondary particle
diameter) of the pigment reached 95 nm. The dispersion time was
about 1 hour.
(Addition Resin)
The glass beads were then removed from the dispersion thus
obtained. To the dispersion were then added 7.2 parts of a 50%
aqueous emulsion of Vinyl Polymer 1 prepared in Synthesis Example 1
(Tg: 130.degree. C.; Mw: 10,000; AV: 53) with stirring to obtain a
dispersion of a surface-treated perylene scarlet pigment (surface
tension: 31 mN/m).
In Example 20, a resin was added after the dispersion step to
prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 20 parts of the dispersion of surface-treated perylene scarlet
pigment obtained in Example 20 (2) were gradually added 0.4 part of
Surfynol TG (trade name, produced by Air Products Co., Ltd.), 1.6
parts of propylene glycol mono-n-butyl ether, 5 parts of
2-pyrrolidone, 5 parts of glycerin, 10 parts of diethylene glycol,
and 58 parts of ion-exchanged water with stirring to obtain the ink
of Example 20. The formulation of the ink will be shown in detail
below.
Surface-treated perylene scarlet pigment of Example 20 (1) 4.0% (as
calculated in terms of solid content) Joncryl 682 0.4% Vinyl
Polymer 1 3.6% (as calculated in terms of solid content) Surfynol
61 0.2% Surfynol 465 0.2% Surfynol TG 0.4% Propylene glycol
mono-n-butyl ether 2.0% 2-Pyrrolidone 5.0% Glycerin 5.0% Diethylene
glycol 10.0% Triethanolamine 0.6% Ion-exchanged water Balance
(The amount of the surface-treated perylene scarlet pigment,
Joncryl 682, Vinyl Polymer 1, Surfynol 61, Surfynol 465, propylene
glycol mono-n-butyl ether, triethanolamine, and ion-exchanged water
in the ink composition include that added as components of the
dispersion of surface-treated perylene scarlet pigment)
Example 21
(1) Preparation of Surface-treated Pigment: C.I. Pigment Orange
36
(Surface Treatment Step)
20 parts of abenzimidazolone orange pigment (C.I. pigment orange
36) which had been previously finely ground and 62 parts of
p-amino-N-ethylpyridinium bromide were dispersed in 150 parts of
water. To the mixture were then added dropwise 32 parts of nitric
acid. The mixture was then stirred at a temperature of 75.degree.
C. for 5 minutes. To the mixture was then added an aqueous solution
of sodium nitrite. The mixture was further stirred for 2 hours, and
then repeatedly rinsed and filtered to obtain a slurry of a
surface-treated benzimidazolone orange pigment having an
N-ethylpyridyl group introduced therein with the interposition of
phenyl group.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 50 parts of the surface-treated benzimidazolone orange pigment
obtained in Example 21 (1) were added 1 part of Hitenol N07
(produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a wetting agent,
10 parts of Joncryl 586 (trade name of styrene-acrylic acid
copolymer which is an alkali-soluble resin produced by Johnson
Polymer Co., Ltd.; Tg: 63.degree. C.; Mw: 3,100; AV: 105) as a
resin, 8 parts of triethanolamine as a neutralizing agent, and 31
parts of ion-exchanged water. The mixture was then subjected to
dispersion by means of a paint shaker (using zirconia beads;
percent bead packing: 60%; medium diameter: 1.7 mm) until the
average particle diameter (secondary particle diameter) of the
pigment reached 110 nm to obtain a surface-treated benzimidazolone
orange pigment dispersion (surface tension: 39 mN/m). The
dispersion time was about 3 hours.
In Example 21, a resin was added at the dispersion step to prepare
a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
To 10 parts of the dispersion of surface-treated benzimidazolone
orange pigment obtained in Example 21 (2) were gradually added 1
part of Surfynol 465 (produced by Air Products Co., Ltd.), 15 parts
of glycerin, and 74 parts of ion-exchanged water with stirring to
obtain the ink of Example 21. The formulation of the ink will be
shown in detail below.
Surface-treated benzimidazolone orange pigment of Example 21 (1)
5.0% (as calculated in terms of solid content) Joncryl 586 1.0%
Surfynol 465 1.0% Hitenol N07 0.1% Glycerin 15.0% Triethanolamine
0.5% Ion-exchanged water Balance
(The amount of the surface-treated benzimidazolone orange pigment,
Joncryl 586, Hitenol N07, triethanolamine, and ion-exchanged water
in the ink composition include that added as components of the
dispersion of surface-treated benzimidazolone orange pigment)
Comparative Example 1
(1) Preparation of Surface-treated Pigment: Carbon Black
(Surface Treatment Step)
In Comparative Example 1, as a surface-treated pigment there was
used the surface-treated carbon black pigment prepared in Example 1
(1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated carbon black pigment obtained in
Example 1 (1) were added 2.5 parts of Surfynol 465 (trade name,
produced by Air Products Inc.) as a wetting agent, 12.5 parts of
triethanolamine as a neutralizing agent, and 65 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 100
nm to obtain a dispersion of a surface-treated carbon black pigment
having a sulfur-containing dispersibility-providing group such as
sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 38 mN/m) The dispersion time was about 1
hour.
In Comparative Example 1, no resins were added to prepare a pigment
dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Comparative Example 1, to 40 parts of the dispersion of
surface-treated carbon black pigment obtained in Example 1 (2) were
gradually added 10 parts of triethylene glycol mono-n-butyl ether,
15 parts of glycerin, 2.5 parts of 1,5-pentanediol, and 32.5 parts
of ion-exchanged water with stirring to obtain the ink of
Comparative Example 1 (black ink). The formulation of the ink will
be shown in detail below.
Surface-treated carbon black pigment of Example 1 (1) 8.0% (as
calculated in terms of solid content) Surfynoyl 465 1.0%
Triethylene glycol monobutyl ether 10.0% Glycerin 15.0%
1,5-Pentanediol 2.5% Triethanolamine 5.0% Ion-exchanged water
Balance
(The amount of the surface-treated carbon black pigment, Surfynol
465, triethanolamine, and ion-exchanged water in the ink
composition include that added as components of the dispersion of
surface-treated carbon black pigment)
In Comparative Example 1, no resins were added to prepare an
ink.
Comparative Example 2
(1) Preparation of Surface-treated Pigment: C.I. Pigment blue
15:3
(Surface Treatment Step)
In Comparative Example 2, as a surface-treated pigment there was
used the surface-treated phthalocyanine blue pigment prepared in
Example 4 (1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 20 parts of the surface-treated phthalocyanine blue pigment
obtained in Example 4 (1) were added 5 parts of a methyl
acrylate-methacrylic acid copolymer which is an alkali-soluble
resin (Tg: 35.degree. C.; Mw: 2,000; AV: 110) as a resin, 5 parts
of monoethanolamine as a neutralizing agent, and 70 parts of
ion-exchanged water. The mixture was then subjected to dispersion
by means of a paint shaker (using glass beads; percent bead
packing: 60%; medium diameter: 1.7 mm) until the average particle
diameter (secondary particle diameter) of the pigment reached 130
nm to obtain a dispersion of a surface-treated phthalocyanine blue
pigment having a sulfur-containing dispersibility-providing group
such as sulfinic acid group (SO.sub.2.sup.-) and sulfonic acid
group (SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 56 mN/m). The dispersion time was about 3
hours.
In Comparative Example 2, no wetting agents were added at the
dispersion step to prepare a pigment dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Comparative Example 2, to 30 parts of the dispersion of
surface-treated phthalocyanine blue pigment obtained in Comparative
Example 2 (2) were gradually added 0.8 part of Surfynol 465, 7.5
parts of diethylene glycol mono-n-butyl ether, 10 parts of
glycerin, 5 parts of 1,2-hexanediol, 0.2 part of
trishydroxymethylaminomethane, 0.03 part of hexachlorophene, and
47.07 parts of ion-exchanged water with stirring to obtain the ink
of Comparative Example 2 (cyan ink).
The formulation of the ink will be shown in detail below.
Surface-treated phthalocyanine blue pigment of Example 4 (1) 6.0%
(as calculated in terms of solid content) Methyl
acrylate-methacrylic acid 1.5% copolymer Surfynol 465 0.8%
Diethylene glycol mono-n-butyl ether 7.5% Glycerin 10.0%
1,2-Hexanediol 5.0% Monoethanolamine 1.5%
Trishydroxymethylaminomethane 0.2% Hexachlorophene 0.03%
Ion-exchanged water Balance
(The amount of the surface-treated phthalocyanine blue pigment,
methyl acrylate-methacrylic acid copolymer, monoethanolamine, and
ion-exchanged water in the ink composition include that added as
components of the dispersion of surface-treated phthalocyanine blue
pigment)
Comparative Example 3
(1) Preparation of Surface-treated Pigment: C.I. Pigment Blue
15:3
(Surface Treatment Step)
In Comparative Example 3, as a surface-treated pigment there was
used the surface-treated phthalocyanine blue pigment prepared in
Example 4 (1) as such.
(2) Preparation of Pigment Dispersion
(Dispersion Step)
To 15 parts of the surface-treated phthalocyanine blue pigment
obtained in Example 4 (1) were added 2 parts of monoethanolamine as
a neutralizing agent, and 83 parts of ion-exchanged water. The
mixture was then subjected to dispersion by means of a paint shaker
(using glass beads; percent bead packing: 60%; medium diameter: 1.7
mm) until the average particle diameter (secondary particle
diameter) of the pigment reached 100 nm to obtain a dispersion of a
surface-treated phthalocyanine blue pigment having a
sulfur-containing dispersibility-providing group such as sulfinic
acid group (SO.sub.2.sup.-) and sulfonic acid group
(SO.sub.3.sup.-) directly introduced onto the surface thereof
(surface tension: 70 mN/m). The dispersion time was about 12
hours.
In Comparative Example 3, no wetting agents were added at the
dispersion step and no resins were added to prepare a pigment
dispersion.
(3) Preparation of Ink for Ink Jet Recording Method
In Comparative Example 3, the pigment dispersion obtained in
Example 4 (1) was used to prepare an ink having the same
formulation as disclosed in JP-A-10-110129. The formulation of the
ink will be shown in detail below.
Surface-treated phthalocyanine blue pigment of Example 4 (1) 3.0%
(as calculated in terms of solid content) Joncryl 61J (trade name
of styrene- 0.1% acrylic acid copolymer produced by Johnson Polymer
Co., Ltd. (30.5% aqueous solution); Tg: 70.degree. C.; Mw: 10,000;
AV: 195) Monoethanolamine 0.1% Glycerin 10.0%
N-methyl-2-pyrrolidone 1.0% 1,2-Benzothiazoline-3-one 0.3%
Disodiium ethylenediaminetetraacetate 0.03% Ion-exchanged water
Balance
(The amount of the surface-treated phthalocyanine blue pigment,
monoethanolamine, and ion-exchanged water in the ink composition
include that added as components of the dispersion of
surface-treated phthalocyanine blue pigment prepared in Comparative
Example 3 (2))
The ink of Comparative Example 3 was prepared free of wetting
agent/penetrating agent having an affinity for resins and providing
inks with penetrating power.
Example 22
In Example 22, using the same printer as used in the evaluation of
ink properties described later, a full-color image was printed with
the ink (black) of Example 3, the ink (cyan) of Example 4, the ink
(yellow) of Example 8 and the ink (magenta) of Example 10.
Example 23
In Example 23, using the same printer as used in the evaluation of
ink properties described later, a full-color image was printed with
the ink (black) of Example 1, the ink (cyan) of Example 5, the ink
(yellow) of Example 9and the ink (magenta) of Example 11.
Comparative Example 4
In Comparative Example 4, using the same printer as used in the
evaluation of ink properties described later, a full-color image
was printed with the ink (black) of Example 3, the ink (cyan) of
Comparative Example 3, the ink (yellow) of Example 8 and the ink
(magenta) of Example 10.
The pigment dispersions and inks obtained in Examples 1 to 21 and
Comparative Examples 1 to 3 were then evaluated as follows.
"Storage Stability of Pigment Dispersion and Ink"
The pigment dispersions and inks obtained in Examples 1 to 21 and
Comparative Examples 1 to 3 were each put in a glass sample bottle,
and then stored at a temperature of 60.degree. C. for 1 week and at
a temperature of -20.degree. C. for 1 week. These samples were each
examined for the occurrence of foreign matters and precipitates
before and after storage.
For the evaluation of foreign matters, the ink was filtered through
a twill-woven filter having a pore diameter of 5 .mu.m. The foreign
matters left behind on the filter were then observed under
microscope. For the evaluation of precipitates, the sample bottles
were each visually observed at the bottom thereof.
The results were then judged according to the following
criterion.
Evaluation A: No occurrence of foreign matters and precipitates
Evaluation B: Slight occurrence of foreign matters and precipitates
but to practically acceptable level
Evaluation C: Some occurrence of foreign matters and precipitates
but to practical level
Evaluation D: Remarkable occurrence of foreign matters and
precipitates to unpractical level
"Evaluation of Print"
Using a Type EM-900C ink jet recording printer produced by Seiko
Epson Corporation, and the ink sets of Examples 22 and 23 and
Comparative Example 4, the inks prepared in Examples 1 to 21 and
Comparative Examples 1 to 3 were each subjected to printing test
with respect to dedicated gloss paper and dedicated gloss film
(produced by Seiko Epson Co., Ltd.). The resulting printed matters
and printing conditions were then evaluated according to the
following methods and criterion.
(1) Feathering and Bleeding
The printed images on the recording medium was visually observed
for smudging. The results were then evaluated according to the
following criterion.
Evaluation A: No feathering and no bleeding observed
Evaluation B: Some feathering or bleeding observed on solid area
where monochromatic inks or two or more color inks are imposed on
each other or come in contact with each other
Evaluation C: Some feathering or bleeding observed on dark-colored
area where monochromatic inks or two or more color inks are imposed
on each other or come in contact with each other
Evaluation D: Remarkable feathering or bleeding observed even at
light-colored area
(2) Fixability
The printed images on the recording medium was stored at room
temperature for 10 minutes, and then rubbed with a finger on the
image area. The printed matters were each then visually observed
for "image smearing". The results were then evaluated according to
the following criterion.
Evaluation A: No smearing observed
Evaluation B: Some smearing observed on full-solid area where
monochromatic inks or two or more color inks are imposed on each
other
Evaluation C: Some smearing observed on dark-colored area where
monochromatic inks or two or more color inks are imposed on each
other
Evaluation D: Remarkable smearing observed even at light-colored
area
(3) Gloss
The foregoing printed images on the gloss media were each visually
observed for "gloss". The results were then evaluated according to
the following criterion.
Evaluation A: Uniform gloss all over the image area on any gloss
media
Evaluation B: Partly rough gloss on full-solid area where
monochromatic inks or two or more color inks are imposed on each
other on some gloss media
Evaluation C: Slightly rough gloss on dark-colored area where
monochromatic inks or two or more color inks are imposed on each
other on some gloss media
Evaluation D: Remarkably rough gloss even at light-colored area on
some gloss media
(4) Ejectability
The inks were each visually observed for "ejectability" during the
foregoing printing test. The results were then evaluated according
to the following criterion.
Evaluation A: No defectives such as misdotting and deflected
flying
Evaluation B: Slight occurrence of defectives such as misdotting
and deflected flying, but returned to normal conditions after one
cleaning
Evaluation C: Some occurrence of defectives such as misdotting and
deflected flying, but returned to normal conditions after three or
less repetitions of cleaning
Evaluation D: Frequent occurrence of defectives such as misdotting
and deflected flying, but not returned to normal conditions even
after repeated cleaning
(5) Clogging
After the foregoing printing test, the printer was switched off and
stored for 1 week. The same printing test was done again. The
ejectability of ink was then visually observed. The results were
then evaluated according to the following criterion.
Evaluation A: Normal printing begins without cleaning
simultaneously with the transmission of print signal to the
printer
Evaluation B: Normal printing begins within three times of
cleaning
Evaluation C: Normal printing begins within six times of
cleaning
Evaluation D: Normal printing doesn't begin even after seven or
more repetitions of cleaning
"Determination of Various Metal Ions"
The pigment dispersions obtained in Examples 1 to 21 and
Comparative Examples 1 to 3 were each measured out in a required
amount, and then subjected to centrifugal separation by a type C-15
centrifugal ultrafiltration apparatus (produced by Millipore Inc.).
As the filter there was used a Type NMwL10000 filter. The
centrifuging was effected at 2,500 G for 60 minutes.
10 mg of the filtrate thus obtained was subjected to oxygen flask
combustion, and then absorbed by a 0.2% aqueous solution of nitric
acid. Subsequently, the specimen was determined for Si, Ca, Mg, Fe,
Cr, and Ni by ion chromatography (column: ionPac AS12A, produced by
Nippon Dionex Co., Ltd.). The results were then evaluated according
to the following criterion:
Evaluation A: Amount of Si, Ca, Mg, Fe, Cr and Ni ions are each not
more than 100 ppm, total amount of these metal ions is not more
than 600 ppm
Evaluation B: Some of Si, Ca, Mg, Fe, Cr and Ni ions are present in
an amount of about 100 ppm, total amount of these metal ions is not
more than 600 ppm
Evaluation C: Some of Si, Ca, Mg, Fe, Cr and Ni ions are present in
an amount of about 100 ppm, total amount of these metal ions is
about 600 ppm
Evaluation D: Some of Si, Ca, Mg, Fe, Cr and Ni ions are present in
an amount of more than 100 ppm, total amount of these metal ions is
more than 600 ppm
The results of evaluation are set forth in Table 1.
TABLE 1 Storage Evaluation of print Determi- stability (1) (2) (4)
(5) nation of Disper- Smudg- Fixab- (3) Eject- Clogg- metal sion
Ink ing ility Gloss ability ing ions Example 1 A A A A A A A A
Example 2 A A A B B B A A Example 3 A A A A A A A A Example 4 A A A
A A A A A Example 5 A A A A A A A A Example 6 A A A A B A A A
Example 7 A A A A A A B B Example 8 A A A A A A B B Example 9 A A A
A A A A A Example 10 A A A A A A A A Example 11 A A A A A A A A
Example 12 A A A A A A A B Example 13 B B A A A A B A Example 14 A
A A B B A A A Example 15 A A A B B A A A Example 16 A A A A A A A A
Example 17 B B B B B A B B Example 18 B B B A A A B B Example 19 B
B A B B A B A Example 20 A A A A A A A A Example 21 C B B A A B B C
Example 22 -- -- A A A A B -- Example 23 -- -- A A A A A --
Comparative A A A D D A A A Example 1 comparative C C A C B B C C
Example 2 comparative D D D C C C D D Example 3 Comparative -- -- D
C C C D -- Example 4 (*1) *1: The results of Comparative Example 4
are the results of evaluation of print on the area related to cyan
ink (image area and head nozzle portion).
As mentioned above in detail, the present invention can provide a
pigment dispersion and an ink jet recording ink excellent in
storage stability. The present invention can provide an ink jet
recording ink suitable for use in an ink jet printer having a head
which has a reduced nozzle diameter and is driven at a high
frequency for the late demand for enhancement of image quality and
operation speed. Further, the ink according to the invention can
provide a sharp printed image having little feathering and bleeding
and excellent fixability and gloss even when printed on a glossy
medium requiring print quality which is equal to or higher than
that of photograph.
The pigment dispersion according to the invention and the ink
comprising same can be used for various purposes such as fountain
pen, ball-point pen, felt pen and other writing utensils, coating
compound for use in air brushing or the like and industrial coating
solution besides the foregoing ink jet recording method.
* * * * *